diff --git a/runtime/observatory/lib/app.dart b/runtime/observatory/lib/app.dart
index 15e802dfa51..6212eb3bce6 100644
--- a/runtime/observatory/lib/app.dart
+++ b/runtime/observatory/lib/app.dart
@@ -12,6 +12,9 @@ import 'dart:math' as math;
 import 'package:logging/logging.dart';
 import 'package:observatory/service_html.dart';
 import 'package:observatory/elements.dart';
+import 'package:observatory/mocks.dart';
+import 'package:observatory/models.dart' as M;
+import 'package:observatory/repositories.dart';
 import 'package:observatory/tracer.dart';
 import 'package:observatory/utils.dart';
 import 'package:polymer/polymer.dart';
@@ -21,6 +24,7 @@ export 'package:observatory/utils.dart';
 
 part 'src/app/application.dart';
 part 'src/app/location_manager.dart';
+part 'src/app/notification.dart';
 part 'src/app/page.dart';
 part 'src/app/settings.dart';
 part 'src/app/target_manager.dart';
diff --git a/runtime/observatory/lib/elements.dart b/runtime/observatory/lib/elements.dart
index 52bef150d27..3cef136aec4 100644
--- a/runtime/observatory/lib/elements.dart
+++ b/runtime/observatory/lib/elements.dart
@@ -63,14 +63,18 @@ import 'dart:async';
 import 'package:observatory/src/elements/curly_block.dart';
 import 'package:observatory/src/elements/curly_block_wrapper.dart';
 import 'package:observatory/src/elements/nav/bar.dart';
-import 'package:observatory/src/elements/nav/isolate_menu.dart';
-import 'package:observatory/src/elements/nav/isolate_menu_wrapper.dart';
 import 'package:observatory/src/elements/nav/class_menu.dart';
 import 'package:observatory/src/elements/nav/class_menu_wrapper.dart';
+import 'package:observatory/src/elements/nav/isolate_menu.dart';
+import 'package:observatory/src/elements/nav/isolate_menu_wrapper.dart';
 import 'package:observatory/src/elements/nav/menu.dart';
 import 'package:observatory/src/elements/nav/menu_wrapper.dart';
 import 'package:observatory/src/elements/nav/menu_item.dart';
 import 'package:observatory/src/elements/nav/menu_item_wrapper.dart';
+import 'package:observatory/src/elements/nav/notify.dart';
+import 'package:observatory/src/elements/nav/notify_wrapper.dart';
+import 'package:observatory/src/elements/nav/notify_event.dart';
+import 'package:observatory/src/elements/nav/notify_exception.dart';
 import 'package:observatory/src/elements/nav/refresh.dart';
 import 'package:observatory/src/elements/nav/refresh_wrapper.dart';
 import 'package:observatory/src/elements/nav/top_menu.dart';
@@ -85,10 +89,13 @@ export 'package:observatory/src/elements/helpers/rendering_queue.dart';
 
 export 'package:observatory/src/elements/curly_block.dart';
 export 'package:observatory/src/elements/nav/bar.dart';
-export 'package:observatory/src/elements/nav/isolate_menu.dart';
 export 'package:observatory/src/elements/nav/class_menu.dart';
+export 'package:observatory/src/elements/nav/isolate_menu.dart';
 export 'package:observatory/src/elements/nav/menu.dart';
 export 'package:observatory/src/elements/nav/menu_item.dart';
+export 'package:observatory/src/elements/nav/notify.dart';
+export 'package:observatory/src/elements/nav/notify_event.dart';
+export 'package:observatory/src/elements/nav/notify_exception.dart';
 export 'package:observatory/src/elements/nav/refresh.dart';
 export 'package:observatory/src/elements/nav/top_menu.dart';
 export 'package:observatory/src/elements/nav/vm_menu.dart';
@@ -101,14 +108,18 @@ Future initElements() async {
   CurlyBlockElement.tag.ensureRegistration();
   CurlyBlockElementWrapper.tag.ensureRegistration();
   NavBarElement.tag.ensureRegistration();
-  NavIsolateMenuElement.tag.ensureRegistration();
-  NavIsolateMenuElementWrapper.tag.ensureRegistration();
   NavClassMenuElement.tag.ensureRegistration();
   NavClassMenuElementWrapper.tag.ensureRegistration();
+  NavIsolateMenuElement.tag.ensureRegistration();
+  NavIsolateMenuElementWrapper.tag.ensureRegistration();
   NavMenuElement.tag.ensureRegistration();
   NavMenuElementWrapper.tag.ensureRegistration();
   NavMenuItemElement.tag.ensureRegistration();
   NavMenuItemElementWrapper.tag.ensureRegistration();
+  NavNotifyElement.tag.ensureRegistration();
+  NavNotifyElementWrapper.tag.ensureRegistration();
+  NavNotifyEventElement.tag.ensureRegistration();
+  NavNotifyExceptionElement.tag.ensureRegistration();
   NavRefreshElement.tag.ensureRegistration();
   NavRefreshElementWrapper.tag.ensureRegistration();
   NavTopMenuElement.tag.ensureRegistration();
diff --git a/runtime/observatory/lib/elements.html b/runtime/observatory/lib/elements.html
index 89aa4a10a85..bcf420b0ee2 100644
--- a/runtime/observatory/lib/elements.html
+++ b/runtime/observatory/lib/elements.html
@@ -37,7 +37,6 @@
 <link rel="import" href="src/elements/objectpool_view.html">
 <link rel="import" href="src/elements/objectstore_view.html">
 <link rel="import" href="src/elements/observatory_application.html">
-<link rel="import" href="src/elements/observatory_element.html">
 <link rel="import" href="src/elements/persistent_handles.html">
 <link rel="import" href="src/elements/ports.html">
 <link rel="import" href="src/elements/script_inset.html">
diff --git a/runtime/observatory/lib/mocks.dart b/runtime/observatory/lib/mocks.dart
index c157b2dbea2..167fea76598 100644
--- a/runtime/observatory/lib/mocks.dart
+++ b/runtime/observatory/lib/mocks.dart
@@ -4,10 +4,20 @@
 
 library mocks;
 
+import 'dart:async';
+
 import 'package:observatory/models.dart' as M;
 
+part 'src/mocks/exceptions/connection_exception.dart';
+
+part 'src/mocks/objects/error.dart';
 part 'src/mocks/objects/event.dart';
 part 'src/mocks/objects/class.dart';
 part 'src/mocks/objects/isolate.dart';
+part 'src/mocks/objects/notification.dart';
+part 'src/mocks/objects/script.dart';
+part 'src/mocks/objects/source_location.dart';
 part 'src/mocks/objects/target.dart';
 part 'src/mocks/objects/vm.dart';
+
+part 'src/mocks/repositories/notification.dart';
diff --git a/runtime/observatory/lib/models.dart b/runtime/observatory/lib/models.dart
index e535b1e07a8..c047e9c9c6e 100644
--- a/runtime/observatory/lib/models.dart
+++ b/runtime/observatory/lib/models.dart
@@ -4,9 +4,25 @@
 
 library models;
 
-part 'src/models/objects/event.dart';
+import 'dart:async';
+
+part 'src/models/exceptions.dart';
+
 part 'src/models/objects/class.dart';
+part 'src/models/objects/breakpoint.dart';
+part 'src/models/objects/error.dart';
+part 'src/models/objects/event.dart';
+part 'src/models/objects/extension_data.dart';
+part 'src/models/objects/frame.dart';
+part 'src/models/objects/instance.dart';
 part 'src/models/objects/isolate.dart';
+part 'src/models/objects/library.dart';
+part 'src/models/objects/notification.dart';
 part 'src/models/objects/object.dart';
+part 'src/models/objects/script.dart';
+part 'src/models/objects/source_location.dart';
 part 'src/models/objects/target.dart';
+part 'src/models/objects/timeline_event.dart';
 part 'src/models/objects/vm.dart';
+
+part 'src/models/repositories/notification.dart';
diff --git a/runtime/observatory/lib/repositories.dart b/runtime/observatory/lib/repositories.dart
new file mode 100644
index 00000000000..5e333ad6302
--- /dev/null
+++ b/runtime/observatory/lib/repositories.dart
@@ -0,0 +1,10 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library repositories;
+
+import 'dart:async';
+import 'package:observatory/models.dart' as M;
+
+part 'src/repositories/notification.dart';
diff --git a/runtime/observatory/lib/src/app/application.dart b/runtime/observatory/lib/src/app/application.dart
index f2096252ec2..b37eda2750e 100644
--- a/runtime/observatory/lib/src/app/application.dart
+++ b/runtime/observatory/lib/src/app/application.dart
@@ -4,20 +4,12 @@
 
 part of app;
 
-class Notification {
-  Notification.fromEvent(this.event);
-  Notification.fromException(this.exception, this.stacktrace);
-
-  ServiceEvent event;
-  var exception;
-  var stacktrace;
-}
-
 /// The observatory application. Instances of this are created and owned
 /// by the observatory_application custom element.
 class ObservatoryApplication extends Observable {
   static ObservatoryApplication app;
   final RenderingQueue queue = new RenderingQueue();
+  final NotificationRepository notifications = new NotificationRepository();
   final _pageRegistry = new List<Page>();
   LocationManager _locationManager;
   LocationManager get locationManager => _locationManager;
@@ -32,7 +24,7 @@ class ObservatoryApplication extends Observable {
     }
     if (_vm != null) {
       // Disconnect from current VM.
-      notifications.clear();
+      notifications.deleteAll();
       _vm.disconnect();
     }
     if (vm != null) {
@@ -42,7 +34,7 @@ class ObservatoryApplication extends Observable {
         if (vm is WebSocketVM) {
           targets.add(vm.target);
         }
-        _removeDisconnectEvents();
+        notifications.deleteDisconnectEvents();
       });
 
       vm.onDisconnect.then((String reason) {
@@ -51,8 +43,8 @@ class ObservatoryApplication extends Observable {
           return;
         }
         notifications.add(
-            new Notification.fromEvent(
-                new ServiceEvent.connectionClosed(reason)));
+            new EventNotification.fromServiceEvent(
+              new ServiceEvent.connectionClosed(reason)));
       });
 
       vm.listenEventStream(VM.kIsolateStream, _onEvent);
@@ -66,8 +58,6 @@ class ObservatoryApplication extends Observable {
   TraceViewElement _traceView = null;
 
   @reflectable ServiceObject lastErrorOrException;
-  @observable ObservableList<Notification> notifications =
-      new ObservableList<Notification>();
 
   void _initOnce() {
     assert(app == null);
@@ -78,15 +68,6 @@ class ObservatoryApplication extends Observable {
     locationManager._visit();
   }
 
-  void removePauseEvents(Isolate isolate) {
-    notifications.removeWhere((notification) {
-        var event = notification.event;
-        return (event != null &&
-                event.isolate == isolate &&
-                event.isPauseEvent);
-      });
-  }
-
   void _onEvent(ServiceEvent event) {
     assert(event.kind != ServiceEvent.kNone);
 
@@ -103,12 +84,12 @@ class ObservatoryApplication extends Observable {
         break;
 
       case ServiceEvent.kIsolateReload:
-        notifications.add(new Notification.fromEvent(event));
+        notifications.add(new EventNotification.fromServiceEvent(event));
         break;
 
       case ServiceEvent.kIsolateExit:
       case ServiceEvent.kResume:
-        removePauseEvents(event.isolate);
+        notifications.deletePauseEvents(isolate: event.isolate);
         break;
 
       case ServiceEvent.kPauseStart:
@@ -116,12 +97,12 @@ class ObservatoryApplication extends Observable {
       case ServiceEvent.kPauseBreakpoint:
       case ServiceEvent.kPauseInterrupted:
       case ServiceEvent.kPauseException:
-        removePauseEvents(event.isolate);
-        notifications.add(new Notification.fromEvent(event));
+        notifications.deletePauseEvents(isolate: event.isolate);
+        notifications.add(new EventNotification.fromServiceEvent(event));
         break;
 
       case ServiceEvent.kInspect:
-        notifications.add(new Notification.fromEvent(event));
+        notifications.add(new EventNotification.fromServiceEvent(event));
         break;
 
       default:
@@ -220,14 +201,6 @@ class ObservatoryApplication extends Observable {
     _initOnce();
   }
 
-  void _removeDisconnectEvents() {
-    notifications.removeWhere((notification) {
-        var event = notification.event;
-        return (event != null &&
-                event.kind == ServiceEvent.kConnectionClosed);
-      });
-  }
-
   loadCrashDump(Map crashDump) {
     this.vm = new FakeVM(crashDump['result']);
     app.locationManager.go('#/vm');
@@ -243,7 +216,7 @@ class ObservatoryApplication extends Observable {
 
     // TODO(turnidge): Report this failure via analytics.
     Logger.root.warning('Caught exception: ${e}\n${st}');
-    notifications.add(new Notification.fromException(e, st));
+    notifications.add(new ExceptionNotification(e, stacktrace: st));
   }
 
   // This map keeps track of which curly-blocks have been expanded by the user.
diff --git a/runtime/observatory/lib/src/app/location_manager.dart b/runtime/observatory/lib/src/app/location_manager.dart
index 577cb92101c..64ea764f927 100644
--- a/runtime/observatory/lib/src/app/location_manager.dart
+++ b/runtime/observatory/lib/src/app/location_manager.dart
@@ -54,6 +54,11 @@ class LocationManager extends Observable {
   /// Update the application location. After this function returns,
   /// [uri] and [debugArguments] will be updated.
   _updateApplicationLocation(String url) {
+    if (url == makeLink('/vm-connect')) {
+      // When we go to the vm-connect page, drop all notifications.
+      _app.notifications.deleteAll();
+    }
+
     // Chop off leading '#'.
     if (url.startsWith('#')) {
       url = url.substring(1);
@@ -115,11 +120,6 @@ class LocationManager extends Observable {
       url = makeLink('/vm-connect');
     }
 
-    if (url == makeLink('/vm-connect')) {
-      // When we go to the vm-connect page, drop all notifications.
-      _app.notifications.clear();
-    }
-
     if (addToBrowserHistory) {
       _addToBrowserHistory(url);
     }
diff --git a/runtime/observatory/lib/src/app/notification.dart b/runtime/observatory/lib/src/app/notification.dart
new file mode 100644
index 00000000000..b95c34e226f
--- /dev/null
+++ b/runtime/observatory/lib/src/app/notification.dart
@@ -0,0 +1,115 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of app;
+
+class ExceptionNotification implements M.ExceptionNotification {
+  final Exception exception;
+  /// [optional]
+  final StackTrace stacktrace;
+  ExceptionNotification(this.exception, {this.stacktrace});
+}
+
+class EventNotification implements M.EventNotification {
+  final M.Event event;
+  EventNotification(this.event);
+  factory EventNotification.fromServiceEvent(ServiceEvent event) {
+    M.Event e;
+    switch(event.kind) {
+      case ServiceEvent.kVMUpdate:
+        e = new VMUpdateEventMock(timestamp: event.timestamp, vm: event.vm);
+        break;
+      case ServiceEvent.kIsolateStart:
+        e = new IsolateStartEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kIsolateRunnable:
+        e = new IsolateRunnableEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kIsolateExit:
+        e = new IsolateExitEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kIsolateUpdate:
+        e = new IsolateUpdateEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kIsolateReload:
+        // TODO(bernaschina) add error: realoadError.
+        e = new IsolateRealodEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kServiceExtensionAdded:
+        e = new ServiceExtensionAddedEventMock(timestamp: event.timestamp,
+            isolate: event.isolate, extensionRPC: event.extensionRPC);
+        break;
+      case ServiceEvent.kPauseStart:
+        e = new PauseStartEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kPauseExit:
+        e = new PauseExitEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kPauseBreakpoint:
+        // TODO(cbernaschina) add pauseBreakpoints.
+        e = new PauseBreakpointEventMock(timestamp: event.timestamp,
+            isolate: event.isolate, breakpoint: event.breakpoint,
+            pauseBreakpoints: const <M.Breakpoint>[],
+            topFrame: event.topFrame,
+            atAsyncSuspension: event.atAsyncSuspension);
+        break;
+      case ServiceEvent.kPauseInterrupted:
+        e = new PauseInterruptedEventMock(timestamp: event.timestamp,
+            isolate: event.isolate, topFrame: event.topFrame,
+            atAsyncSuspension: event.atAsyncSuspension);
+        break;
+      case ServiceEvent.kPauseException:
+        // TODO(cbernaschina) add exception.
+        e = new PauseExceptionEventMock(timestamp: event.timestamp,
+            isolate: event.isolate, topFrame: event.topFrame);
+        break;
+      case ServiceEvent.kNone:
+        e = new NoneEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kResume:
+        e = new ResumeEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kBreakpointAdded:
+        e = new BreakpointAddedEventMock(timestamp: event.timestamp,
+            isolate: event.isolate, breakpoint: event.breakpoint);
+        break;
+      case ServiceEvent.kBreakpointResolved:
+        e = new BreakpointResolvedEventMock(timestamp: event.timestamp,
+            isolate: event.isolate, breakpoint: event.breakpoint);
+        break;
+      case ServiceEvent.kBreakpointRemoved:
+        e = new BreakpointRemovedEventMock(timestamp: event.timestamp,
+            isolate: event.isolate, breakpoint: event.breakpoint);
+        break;
+      case ServiceEvent.kGC:
+        e = new GCEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kInspect:
+       // TODO(cbernaschina) add inspectee: event.inspectee.
+        e = new InspectEventMock(timestamp: event.timestamp,
+            isolate: event.isolate);
+        break;
+      case ServiceEvent.kConnectionClosed:
+        e = new ConnectionClockedEventMock(timestamp: event.timestamp,
+            reason: event.reason);
+        break;
+      case ServiceEvent.kExtension:
+        e = new ExtensionEventMock(timestamp: event.timestamp,
+            isolate: event.isolate, extensionKind: event.extensionKind,
+            extensionData: event.extensionData);
+        break;
+    }
+    return new EventNotification(e);
+  }
+}
diff --git a/runtime/observatory/lib/src/elements/action_link.html b/runtime/observatory/lib/src/elements/action_link.html
index 46ced3420c9..1b0438b1f2e 100644
--- a/runtime/observatory/lib/src/elements/action_link.html
+++ b/runtime/observatory/lib/src/elements/action_link.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="action-link" extends="observatory-element">
+
+<polymer-element name="action-link">
   <template>
     <style>
       .idle {
diff --git a/runtime/observatory/lib/src/elements/class_ref.html b/runtime/observatory/lib/src/elements/class_ref.html
index 190d25acef1..1ffe1d16f87 100644
--- a/runtime/observatory/lib/src/elements/class_ref.html
+++ b/runtime/observatory/lib/src/elements/class_ref.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="class-ref" extends="service-ref">
+<polymer-element name="class-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/class_tree.html b/runtime/observatory/lib/src/elements/class_tree.html
index 7a366df7296..4326b00d178 100644
--- a/runtime/observatory/lib/src/elements/class_tree.html
+++ b/runtime/observatory/lib/src/elements/class_tree.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="class_ref.html">
 
-<polymer-element name="class-tree" extends="observatory-element">
+<polymer-element name="class-tree">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/class_view.html b/runtime/observatory/lib/src/elements/class_view.html
index 37ce9b030f2..7a8f48dcd78 100644
--- a/runtime/observatory/lib/src/elements/class_view.html
+++ b/runtime/observatory/lib/src/elements/class_view.html
@@ -8,11 +8,11 @@
 <link rel="import" href="instance_ref.html">
 <link rel="import" href="library_ref.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 
-<polymer-element name="class-view" extends="observatory-element">
+<polymer-element name="class-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/code_ref.html b/runtime/observatory/lib/src/elements/code_ref.html
index c20fdb5d1d5..4a8c7f5a628 100644
--- a/runtime/observatory/lib/src/elements/code_ref.html
+++ b/runtime/observatory/lib/src/elements/code_ref.html
@@ -1,7 +1,7 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="code-ref" extends="service-ref">
+<polymer-element name="code-ref">
   <template><link rel="stylesheet" href="css/shared.css"></template>
 </polymer-element>
 
diff --git a/runtime/observatory/lib/src/elements/code_view.html b/runtime/observatory/lib/src/elements/code_view.html
index 824260a4c3b..2ead0eec716 100644
--- a/runtime/observatory/lib/src/elements/code_view.html
+++ b/runtime/observatory/lib/src/elements/code_view.html
@@ -1,11 +1,11 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="script_ref.html">
 
-<polymer-element name="code-view" extends="observatory-element">
+<polymer-element name="code-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/context_ref.html b/runtime/observatory/lib/src/elements/context_ref.html
index a0d210b88ef..9beb691dbaa 100644
--- a/runtime/observatory/lib/src/elements/context_ref.html
+++ b/runtime/observatory/lib/src/elements/context_ref.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="context-ref" extends="service-ref">
+<polymer-element name="context-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <span>
diff --git a/runtime/observatory/lib/src/elements/context_view.html b/runtime/observatory/lib/src/elements/context_view.html
index 0b76ecdccfc..7517e14ed0a 100644
--- a/runtime/observatory/lib/src/elements/context_view.html
+++ b/runtime/observatory/lib/src/elements/context_view.html
@@ -3,12 +3,12 @@
 <link rel="import" href="field_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="object_common.html">
 <link rel="import" href="context_ref.html">
 
-<polymer-element name="context-view" extends="observatory-element">
+<polymer-element name="context-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/cpu_profile.html b/runtime/observatory/lib/src/elements/cpu_profile.html
index db7a8636e87..d57494c1700 100644
--- a/runtime/observatory/lib/src/elements/cpu_profile.html
+++ b/runtime/observatory/lib/src/elements/cpu_profile.html
@@ -2,10 +2,10 @@
 <link rel="import" href="code_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="sliding_checkbox.html">
 
-<polymer-element name="sample-buffer-control" extends="observatory-element">
+<polymer-element name="sample-buffer-control">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -114,7 +114,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="stack-trace-tree-config" extends="observatory-element">
+<polymer-element name="stack-trace-tree-config">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -181,7 +181,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="cpu-profile-tree" extends="observatory-element">
+<polymer-element name="cpu-profile-tree">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -253,7 +253,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="cpu-profile-virtual-tree" extends="observatory-element">
+<polymer-element name="cpu-profile-virtual-tree">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -276,7 +276,7 @@
 </polymer-element>
 
 
-<polymer-element name="cpu-profile-table" extends="observatory-element">
+<polymer-element name="cpu-profile-table">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
@@ -491,7 +491,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="cpu-profile" extends="observatory-element">
+<polymer-element name="cpu-profile">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/css/shared.css b/runtime/observatory/lib/src/elements/css/shared.css
index e1a400dd09c..75b35ced4cd 100644
--- a/runtime/observatory/lib/src/elements/css/shared.css
+++ b/runtime/observatory/lib/src/elements/css/shared.css
@@ -359,6 +359,81 @@ body.busy, body.busy * {
   -webkit-animation: shake 0.5s;
 }
 
+/* nav-notify */
+/* TODO(cbernaschina) fix nav-notify-ref-wrapped to nav-notify-ref when wrapper
+removed */
+nav-notify-wrapped > div {
+  float: right;
+}
+nav-notify-wrapped > div > div {
+  display: block;
+  position: absolute;
+  top: 98%;
+  right: 0;
+  margin: 0;
+  padding: 0;
+  width: auto;
+  z-index: 1000;
+  background: none;
+}
+
+/* nav-exception & nav-event */
+
+nav-exception > div, nav-event > div {
+  position: relative;
+  padding: 16px;
+  margin-top: 10px;
+  margin-right: 10px;
+  padding-right: 25px;
+  width: 500px;
+  color: #ddd;
+  background: rgba(0,0,0,.6);
+  border: solid 2px white;
+  box-shadow: 0 0 5px black;
+  border-radius: 5px;
+  animation: fadein 1s;
+}
+
+nav-exception *, nav-event * {
+  color: #ddd;
+  font-size: 12px;
+}
+
+nav-exception > div > a, nav-event > div > a {
+  color: white;
+  text-decoration: none;
+}
+
+nav-exception > div > a:hover, nav-event > div > a:hover {
+  text-decoration: underline;
+}
+
+nav-exception > div > div {
+  margin-left:20px;
+  white-space: pre
+}
+
+nav-exception > div > button, nav-event > div > button {
+  background: transparent;
+  border: none;
+  position: absolute;
+  display: block;
+  top: 4px;
+  right: 4px;
+  height: 18px;
+  width: 18px;
+  line-height: 16px;
+  border-radius: 9px;
+  color: white;
+  font-size: 18px;
+  cursor: pointer;
+  text-align: center;
+}
+
+nav-exception > div > button:hover, nav-event > div > button:hover {
+  background: rgba(255,255,255,0.5);
+}
+
 /* nav-refresh */
 /* TODO(cbernaschina) fix nav-refresh-wrapped to nav-refresh when wrapper
 removed */
diff --git a/runtime/observatory/lib/src/elements/debugger.html b/runtime/observatory/lib/src/elements/debugger.html
index 3b71b5a14c4..49383dd88f9 100644
--- a/runtime/observatory/lib/src/elements/debugger.html
+++ b/runtime/observatory/lib/src/elements/debugger.html
@@ -2,7 +2,7 @@
 <link rel="import" href="function_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="eval_link.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 
@@ -72,7 +72,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="debugger-page" extends="observatory-element">
+<polymer-element name="debugger-page">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -134,7 +134,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="debugger-stack" extends="observatory-element">
+<polymer-element name="debugger-stack">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -185,7 +185,7 @@
 </polymer-element>
 
 
-<polymer-element name="debugger-frame" extends="observatory-element">
+<polymer-element name="debugger-frame">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -301,7 +301,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="debugger-message" extends="observatory-element">
+<polymer-element name="debugger-message">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -406,7 +406,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="debugger-console" extends="observatory-element">
+<polymer-element name="debugger-console">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -445,7 +445,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="debugger-input" extends="observatory-element">
+<polymer-element name="debugger-input">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/error_ref.html b/runtime/observatory/lib/src/elements/error_ref.html
index 1857b71d679..a1320394902 100644
--- a/runtime/observatory/lib/src/elements/error_ref.html
+++ b/runtime/observatory/lib/src/elements/error_ref.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="error-ref" extends="service-ref">
+<polymer-element name="error-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/error_view.html b/runtime/observatory/lib/src/elements/error_view.html
index 24c33a9f7e7..4cbcae19197 100644
--- a/runtime/observatory/lib/src/elements/error_view.html
+++ b/runtime/observatory/lib/src/elements/error_view.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="error-view" extends="observatory-element">
+
+<polymer-element name="error-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/eval_box.html b/runtime/observatory/lib/src/elements/eval_box.html
index f01a995a19d..eb1e639d5c4 100644
--- a/runtime/observatory/lib/src/elements/eval_box.html
+++ b/runtime/observatory/lib/src/elements/eval_box.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="instance_ref.html">
 <link rel="import" href="error_ref.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="eval-box" extends="observatory-element">
+
+<polymer-element name="eval-box">
   <template>
     <style>
       .textbox {
diff --git a/runtime/observatory/lib/src/elements/eval_link.html b/runtime/observatory/lib/src/elements/eval_link.html
index 1fdb584b806..38d2981e965 100644
--- a/runtime/observatory/lib/src/elements/eval_link.html
+++ b/runtime/observatory/lib/src/elements/eval_link.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="instance_ref.html">
 <link rel="import" href="error_ref.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="eval-link" extends="observatory-element">
+
+<polymer-element name="eval-link">
   <template>
     <style>
       .idle {
diff --git a/runtime/observatory/lib/src/elements/field_ref.html b/runtime/observatory/lib/src/elements/field_ref.html
index 762362a0611..a593d313f9d 100644
--- a/runtime/observatory/lib/src/elements/field_ref.html
+++ b/runtime/observatory/lib/src/elements/field_ref.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="field-ref" extends="service-ref">
+<polymer-element name="field-ref">
   <template>
   <link rel="stylesheet" href="css/shared.css">
     <span>
diff --git a/runtime/observatory/lib/src/elements/field_view.html b/runtime/observatory/lib/src/elements/field_view.html
index 7b43591584d..bfa243b40fc 100644
--- a/runtime/observatory/lib/src/elements/field_view.html
+++ b/runtime/observatory/lib/src/elements/field_view.html
@@ -4,9 +4,9 @@
 <link rel="import" href="library_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="script_ref.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="field-view" extends="observatory-element">
+
+<polymer-element name="field-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/flag_list.html b/runtime/observatory/lib/src/elements/flag_list.html
index b4796f27adb..b39c174d8e5 100644
--- a/runtime/observatory/lib/src/elements/flag_list.html
+++ b/runtime/observatory/lib/src/elements/flag_list.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="flag-list" extends="observatory-element">
+
+<polymer-element name="flag-list">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
@@ -40,7 +40,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="flag-item" extends="observatory-element">
+<polymer-element name="flag-item">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <span style="color:#aaa">// {{ flag['comment'] }}</span>
diff --git a/runtime/observatory/lib/src/elements/function_ref.html b/runtime/observatory/lib/src/elements/function_ref.html
index c9499b39a72..4669386a22e 100644
--- a/runtime/observatory/lib/src/elements/function_ref.html
+++ b/runtime/observatory/lib/src/elements/function_ref.html
@@ -2,7 +2,7 @@
 <link rel="import" href="class_ref.html">
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="function-ref" extends="service-ref">
+<polymer-element name="function-ref">
   <template><link rel="stylesheet" href="css/shared.css"></template>
 </polymer-element>
 
diff --git a/runtime/observatory/lib/src/elements/function_view.html b/runtime/observatory/lib/src/elements/function_view.html
index 173b2bf508f..d40944f31ee 100644
--- a/runtime/observatory/lib/src/elements/function_view.html
+++ b/runtime/observatory/lib/src/elements/function_view.html
@@ -3,12 +3,12 @@
 <link rel="import" href="code_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="library_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 
-<polymer-element name="function-view" extends="observatory-element">
+<polymer-element name="function-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/general_error.html b/runtime/observatory/lib/src/elements/general_error.html
index 258e9e6cdd4..7ca0da11495 100644
--- a/runtime/observatory/lib/src/elements/general_error.html
+++ b/runtime/observatory/lib/src/elements/general_error.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="general-error" extends="observatory-element">
+
+<polymer-element name="general-error">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/heap_map.html b/runtime/observatory/lib/src/elements/heap_map.html
index 37491baffc2..714760d9636 100644
--- a/runtime/observatory/lib/src/elements/heap_map.html
+++ b/runtime/observatory/lib/src/elements/heap_map.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="class_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="nav_bar.html">
 
-<polymer-element name="heap-map" extends="observatory-element">
+<polymer-element name="heap-map">
 <template>
   <link rel="stylesheet" href="css/shared.css">
   <style>
diff --git a/runtime/observatory/lib/src/elements/heap_profile.html b/runtime/observatory/lib/src/elements/heap_profile.html
index 438695121fb..a46fd9b18ac 100644
--- a/runtime/observatory/lib/src/elements/heap_profile.html
+++ b/runtime/observatory/lib/src/elements/heap_profile.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="class_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="nav_bar.html">
 
-<polymer-element name="heap-profile" extends="observatory-element">
+<polymer-element name="heap-profile">
 <template>
   <link rel="stylesheet" href="css/shared.css">
   <style>
diff --git a/runtime/observatory/lib/src/elements/heap_snapshot.html b/runtime/observatory/lib/src/elements/heap_snapshot.html
index 30e00fc6125..18dcddb1055 100644
--- a/runtime/observatory/lib/src/elements/heap_snapshot.html
+++ b/runtime/observatory/lib/src/elements/heap_snapshot.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="class_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="nav_bar.html">
 
-<polymer-element name="heap-snapshot" extends="observatory-element">
+<polymer-element name="heap-snapshot">
 <template>
   <link rel="stylesheet" href="css/shared.css">
   <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/icdata_view.html b/runtime/observatory/lib/src/elements/icdata_view.html
index c55a4b624ca..3c16c7b2a79 100644
--- a/runtime/observatory/lib/src/elements/icdata_view.html
+++ b/runtime/observatory/lib/src/elements/icdata_view.html
@@ -5,12 +5,12 @@
 <link rel="import" href="function_ref.html">
 <link rel="import" href="inbound_reference.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="object_common.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="eval_link.html">
 
-<polymer-element name="icdata-view" extends="observatory-element">
+<polymer-element name="icdata-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/inbound_reference.html b/runtime/observatory/lib/src/elements/inbound_reference.html
index 72657d1ad1a..cfda6659fb5 100644
--- a/runtime/observatory/lib/src/elements/inbound_reference.html
+++ b/runtime/observatory/lib/src/elements/inbound_reference.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="field_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="inbound-reference" extends="service-ref">
+<polymer-element name="inbound-reference">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <div>
diff --git a/runtime/observatory/lib/src/elements/instance_ref.html b/runtime/observatory/lib/src/elements/instance_ref.html
index 535ca34ae2a..dffa36cb080 100644
--- a/runtime/observatory/lib/src/elements/instance_ref.html
+++ b/runtime/observatory/lib/src/elements/instance_ref.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="instance-ref" extends="service-ref">
+<polymer-element name="instance-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/instance_view.html b/runtime/observatory/lib/src/elements/instance_view.html
index 266b4d15ea5..f5085ea8f75 100644
--- a/runtime/observatory/lib/src/elements/instance_view.html
+++ b/runtime/observatory/lib/src/elements/instance_view.html
@@ -7,12 +7,12 @@
 <link rel="import" href="function_ref.html">
 <link rel="import" href="inbound_reference.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="object_common.html">
 <link rel="import" href="context_ref.html">
 
-<polymer-element name="instance-view" extends="observatory-element">
+<polymer-element name="instance-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/instructions_view.html b/runtime/observatory/lib/src/elements/instructions_view.html
index 42ac61a6b31..9160a3b2268 100644
--- a/runtime/observatory/lib/src/elements/instructions_view.html
+++ b/runtime/observatory/lib/src/elements/instructions_view.html
@@ -5,12 +5,12 @@
 <link rel="import" href="function_ref.html">
 <link rel="import" href="inbound_reference.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="object_common.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="eval_link.html">
 
-<polymer-element name="instructions-view" extends="observatory-element">
+<polymer-element name="instructions-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/io_view.html b/runtime/observatory/lib/src/elements/io_view.html
index 3c51e53d0ee..ce02305ec7c 100644
--- a/runtime/observatory/lib/src/elements/io_view.html
+++ b/runtime/observatory/lib/src/elements/io_view.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="io-view" extends="observatory-element">
+<polymer-element name="io-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -62,7 +62,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-ref" extends="service-ref">
+<polymer-element name="io-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <template if="{{ ref.type == 'Socket' }}">
@@ -83,7 +83,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-http-server-list-view" extends="observatory-element">
+<polymer-element name="io-http-server-list-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -111,14 +111,14 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-http-server-ref" extends="service-ref">
+<polymer-element name="io-http-server-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <a on-click="{{ goto }}" _href="{{ url }}">{{ name }}</a>
   </template>
 </polymer-element>
 
-<polymer-element name="io-http-server-view" extends="observatory-element">
+<polymer-element name="io-http-server-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -173,14 +173,14 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-http-server-connection-ref" extends="service-ref">
+<polymer-element name="io-http-server-connection-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <a _href="{{ url }}">{{ name }}</a>
   </template>
 </polymer-element>
 
-<polymer-element name="io-http-server-connection-view" extends="observatory-element">
+<polymer-element name="io-http-server-connection-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -215,14 +215,14 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-socket-ref" extends="service-ref">
+<polymer-element name="io-socket-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <a on-click="{{ goto }}" _href="{{ url }}">{{ name }}</a>
   </template>
 </polymer-element>
 
-<polymer-element name="io-socket-list-view" extends="observatory-element">
+<polymer-element name="io-socket-list-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -250,7 +250,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-socket-view" extends="observatory-element">
+<polymer-element name="io-socket-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -346,14 +346,14 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-web-socket-ref" extends="service-ref">
+<polymer-element name="io-web-socket-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <a on-click="{{ goto }}" _href="{{ url }}">{{ name }}</a>
   </template>
 </polymer-element>
 
-<polymer-element name="io-web-socket-list-view" extends="observatory-element">
+<polymer-element name="io-web-socket-list-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -381,7 +381,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-web-socket-view" extends="observatory-element">
+<polymer-element name="io-web-socket-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -408,14 +408,14 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-random-access-file-ref" extends="service-ref">
+<polymer-element name="io-random-access-file-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <a on-click="{{ goto }}" _href="{{ url }}">{{ name }}</a>
   </template>
 </polymer-element>
 
-<polymer-element name="io-random-access-file-list-view" extends="observatory-element">
+<polymer-element name="io-random-access-file-list-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -443,7 +443,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-random-access-file-view" extends="observatory-element">
+<polymer-element name="io-random-access-file-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -478,7 +478,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-process-list-view" extends="observatory-element">
+<polymer-element name="io-process-list-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -506,7 +506,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-process-ref" extends="service-ref">
+<polymer-element name="io-process-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <template if="{{ small }}">
@@ -518,7 +518,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="io-process-view" extends="observatory-element">
+<polymer-element name="io-process-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
diff --git a/runtime/observatory/lib/src/elements/isolate_reconnect.html b/runtime/observatory/lib/src/elements/isolate_reconnect.html
index eec26c20603..1939718a27d 100644
--- a/runtime/observatory/lib/src/elements/isolate_reconnect.html
+++ b/runtime/observatory/lib/src/elements/isolate_reconnect.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="isolate-reconnect" extends="observatory-element">
+
+<polymer-element name="isolate-reconnect">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/isolate_ref.html b/runtime/observatory/lib/src/elements/isolate_ref.html
index edfb3eacdc5..8e1f7f96d1d 100644
--- a/runtime/observatory/lib/src/elements/isolate_ref.html
+++ b/runtime/observatory/lib/src/elements/isolate_ref.html
@@ -1,6 +1,6 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="service_ref.html">
-<polymer-element name="isolate-ref" extends="service-ref">
+<polymer-element name="isolate-ref">
 <template><link rel="stylesheet" href="css/shared.css">
   <a on-click="{{ goto }}" _href="{{ url }}">Isolate {{ ref.number }} ({{ ref.name }})</a>
 </template>
diff --git a/runtime/observatory/lib/src/elements/isolate_summary.html b/runtime/observatory/lib/src/elements/isolate_summary.html
index c089da945cc..42d863e3c5b 100644
--- a/runtime/observatory/lib/src/elements/isolate_summary.html
+++ b/runtime/observatory/lib/src/elements/isolate_summary.html
@@ -2,10 +2,10 @@
 <link rel="import" href="action_link.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="isolate_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
-<polymer-element name="isolate-summary" extends="observatory-element">
+<polymer-element name="isolate-summary">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <div class="flex-row">
@@ -24,7 +24,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="isolate-run-state" extends="observatory-element">
+<polymer-element name="isolate-run-state">
   <template>
     <template if="{{ isolate.paused }}">
       <strong title="{{ isolate.pauseEvent.timestamp.toString() }}">paused</strong>
@@ -44,7 +44,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="isolate-location" extends="observatory-element">
+<polymer-element name="isolate-location">
   <template>
     <template if="{{ isolate.pauseEvent != null }}">
       <template if="{{ isolate.pauseEvent.kind == 'PauseStart' }}">
@@ -88,7 +88,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="isolate-shared-summary" extends="observatory-element">
+<polymer-element name="isolate-shared-summary">
   <template>
     <style>
       .errorBox {
@@ -201,7 +201,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="isolate-counter-chart" extends="observatory-element">
+<polymer-element name="isolate-counter-chart">
   <template>
     <link rel="stylesheet" href="../../../../packages/charted/charts/themes/quantum_theme.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/isolate_view.html b/runtime/observatory/lib/src/elements/isolate_view.html
index 619bbfd2768..7e805aafbe9 100644
--- a/runtime/observatory/lib/src/elements/isolate_view.html
+++ b/runtime/observatory/lib/src/elements/isolate_view.html
@@ -5,11 +5,11 @@
 <link rel="import" href="isolate_summary.html">
 <link rel="import" href="library_ref.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 
-<polymer-element name="isolate-view" extends="observatory-element">
+<polymer-element name="isolate-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/json_view.html b/runtime/observatory/lib/src/elements/json_view.html
index 5aa2a68210a..1bbb097f88e 100644
--- a/runtime/observatory/lib/src/elements/json_view.html
+++ b/runtime/observatory/lib/src/elements/json_view.html
@@ -1,7 +1,7 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
-<polymer-element name="json-view" extends="observatory-element">
+
+<polymer-element name="json-view">
   <template>
     <nav-bar>
       <top-nav-menu last="{{ true }}"></top-nav-menu>
diff --git a/runtime/observatory/lib/src/elements/library_ref.html b/runtime/observatory/lib/src/elements/library_ref.html
index 55861ebfe1a..6e8c7a05a19 100644
--- a/runtime/observatory/lib/src/elements/library_ref.html
+++ b/runtime/observatory/lib/src/elements/library_ref.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="library-ref" extends="service-ref">
+<polymer-element name="library-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/library_view.html b/runtime/observatory/lib/src/elements/library_view.html
index 39c044b40af..c6e280924e6 100644
--- a/runtime/observatory/lib/src/elements/library_view.html
+++ b/runtime/observatory/lib/src/elements/library_view.html
@@ -4,12 +4,12 @@
 <link rel="import" href="field_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="library_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="script_ref.html">
 
-<polymer-element name="library-view" extends="observatory-element">
+<polymer-element name="library-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
diff --git a/runtime/observatory/lib/src/elements/logging.html b/runtime/observatory/lib/src/elements/logging.html
index b9aa92c7b3c..e8015ede647 100644
--- a/runtime/observatory/lib/src/elements/logging.html
+++ b/runtime/observatory/lib/src/elements/logging.html
@@ -2,10 +2,10 @@
 <link rel="import" href="code_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="sliding_checkbox.html">
 
-<polymer-element name="logging-page" extends="observatory-element">
+<polymer-element name="logging-page">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/megamorphiccache_view.html b/runtime/observatory/lib/src/elements/megamorphiccache_view.html
index 89ce9cef421..2d657b86254 100644
--- a/runtime/observatory/lib/src/elements/megamorphiccache_view.html
+++ b/runtime/observatory/lib/src/elements/megamorphiccache_view.html
@@ -5,12 +5,12 @@
 <link rel="import" href="function_ref.html">
 <link rel="import" href="inbound_reference.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="object_common.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="eval_link.html">
 
-<polymer-element name="megamorphiccache-view" extends="observatory-element">
+<polymer-element name="megamorphiccache-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/metrics.html b/runtime/observatory/lib/src/elements/metrics.html
index e9573a05ba9..80c48d29194 100644
--- a/runtime/observatory/lib/src/elements/metrics.html
+++ b/runtime/observatory/lib/src/elements/metrics.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="metrics-page" extends="observatory-element">
+
+<polymer-element name="metrics-page">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
@@ -66,7 +66,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="metric-details" extends="observatory-element">
+<polymer-element name="metric-details">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <div class="content-centered">
@@ -125,7 +125,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="metrics-graph" extends="observatory-element">
+<polymer-element name="metrics-graph">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <link rel="stylesheet" href="../../../../packages/charted/charts/themes/quantum_theme.css">
diff --git a/runtime/observatory/lib/src/elements/nav/notify.dart b/runtime/observatory/lib/src/elements/nav/notify.dart
new file mode 100644
index 00000000000..ba99f014a41
--- /dev/null
+++ b/runtime/observatory/lib/src/elements/nav/notify.dart
@@ -0,0 +1,90 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:html';
+import 'dart:async';
+import 'package:observatory/models.dart' as M;
+import 'package:observatory/src/elements/helpers/tag.dart';
+import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
+import 'package:observatory/src/elements/nav/notify_event.dart';
+import 'package:observatory/src/elements/nav/notify_exception.dart';
+
+class NavNotifyElement extends HtmlElement implements Renderable {
+  static const tag = const Tag<NavNotifyElement>('nav-notify-wrapped',
+          dependencies: const [ NavNotifyEventElement.tag,
+                                NavNotifyExceptionElement.tag ]);
+
+  RenderingScheduler _r;
+
+  Stream<RenderedEvent<NavNotifyElement>> get onRendered => _r.onRendered;
+
+  M.NotificationRepository _repository;
+  StreamSubscription _subscription;
+
+  bool _notifyOnPause;
+  bool get notifyOnPause => _notifyOnPause;
+  set notifyOnPause(bool value) =>
+      _notifyOnPause = _r.checkAndReact(_notifyOnPause, value);
+
+  factory NavNotifyElement(M.NotificationRepository repository,
+                           {bool notifyOnPause: true, RenderingQueue queue}) {
+    assert(repository != null);
+    assert(notifyOnPause != null);
+    NavNotifyElement e = document.createElement(tag.name);
+    e._r = new RenderingScheduler(e, queue: queue);
+    e._repository = repository;
+    e._notifyOnPause = notifyOnPause;
+    return e;
+  }
+
+  NavNotifyElement.created() : super.created();
+
+  @override
+  void attached() {
+    super.attached();
+    _r.enable();
+    _subscription = _repository.onChange.listen((_) => _r.dirty());
+  }
+
+  @override
+  void detached() {
+    super.detached();
+    children = [];
+    _r.disable(notify: true);
+    _subscription.cancel();
+  }
+
+  void render() {
+    children = [
+      new DivElement()
+        ..children = [
+          new DivElement()
+            ..children = _repository.list()
+              .where(_filter).map(_toElement).toList()
+        ]
+    ];
+  }
+
+  bool _filter(M.Notification notification) {
+    if (!_notifyOnPause && notification is M.EventNotification) {
+      return !M.Event.isPauseEvent(notification.event);
+    }
+    return true;
+  }
+
+  HtmlElement _toElement(M.Notification notification) {
+    if (notification is M.EventNotification) {
+      return new NavNotifyEventElement(notification.event, queue: _r.queue)
+          ..onDelete.listen((_) => _repository.delete(notification));
+    } else if (notification is M.ExceptionNotification) {
+      return new NavNotifyExceptionElement(
+              notification.exception, stacktrace: notification.stacktrace,
+              queue: _r.queue)
+          ..onDelete.listen((_) => _repository.delete(notification));
+    } else {
+      assert(false);
+      return new DivElement()..text = 'Invalid Notification Type';
+    }
+  }
+}
diff --git a/runtime/observatory/lib/src/elements/nav/notify_event.dart b/runtime/observatory/lib/src/elements/nav/notify_event.dart
new file mode 100644
index 00000000000..0f75062a9ba
--- /dev/null
+++ b/runtime/observatory/lib/src/elements/nav/notify_event.dart
@@ -0,0 +1,232 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:html';
+import 'dart:async';
+import 'package:observatory/models.dart' as M;
+import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
+import 'package:observatory/src/elements/helpers/tag.dart';
+import 'package:observatory/src/elements/helpers/uris.dart';
+
+class EventDeleteEvent{
+  final M.Event event;
+  EventDeleteEvent(this.event);
+}
+
+class NavNotifyEventElement extends HtmlElement implements Renderable {
+  static const tag = const Tag<NavNotifyEventElement>('nav-event');
+
+  RenderingScheduler _r;
+
+  Stream<RenderedEvent<NavNotifyEventElement>> get onRendered => _r.onRendered;
+
+  final StreamController<EventDeleteEvent> _onDelete =
+      new StreamController<EventDeleteEvent>.broadcast();
+  Stream<EventDeleteEvent> get onDelete => _onDelete.stream;
+
+  M.Event _event;
+  M.Event get event => _event;
+
+  factory NavNotifyEventElement(M.Event event, {RenderingQueue queue}) {
+    assert(event != null);
+    NavNotifyEventElement e = document.createElement(tag.name);
+    e._r = new RenderingScheduler(e, queue: queue);
+    e._event = event;
+    return e;
+  }
+
+  NavNotifyEventElement.created() : super.created();
+
+  @override
+  void attached() {
+    super.attached();
+    _r.enable();
+  }
+
+  @override
+  void detached() {
+    super.detached();
+    children = [];
+    _r.disable(notify: true);
+  }
+
+  void render() {
+    children = [];
+    List<Element> content;
+    if (event is M.PauseStartEvent) {
+      content = _managePauseStartEvent(event as M.PauseStartEvent);
+    } else if (event is M.PauseExitEvent) {
+      content = _managePauseExitEvent(event as M.PauseExitEvent);
+    } else if (event is M.PauseBreakpointEvent) {
+      content = _managePauseBreakpointEvent(event as M.PauseBreakpointEvent);
+    } else if (event is M.PauseInterruptedEvent) {
+      content = _managePauseInterruptedEvent(event as M.PauseInterruptedEvent);
+    } else if (event is M.PauseExceptionEvent) {
+      content = _managePauseExceptionEvent(event as M.PauseExceptionEvent);
+    } else if (event is M.NoneEvent) {
+      content = _manageNoneEvent(event as M.NoneEvent);
+    } else if (event is M.ConnectionClosedEvent) {
+      content = _manageConnectionClosedEvent(event as M.ConnectionClosedEvent);
+    } else if (event is M.InspectEvent) {
+      content = _manageInspectEvent(event as M.InspectEvent);
+    } else if (event is M.IsolateReloadEvent) {
+      content = _manageIsolateReloadEvent(event as M.IsolateReloadEvent);
+    } else {
+      return;
+    }
+    children = [
+      new DivElement()
+        ..children = []
+        ..children.addAll(content)
+        ..children.add(new ButtonElement()..innerHtml = '&times;'
+            ..onClick.map(_toEvent).listen(_delete))
+    ];
+  }
+
+  static List<Element> _managePauseStartEvent(M.PauseStartEvent event) {
+    return [
+      new SpanElement()..text = 'Isolate ',
+      new AnchorElement(
+        href: Uris.inspect(event.isolate))
+        ..text = event.isolate.name,
+      new SpanElement()..text = ' is paused at isolate start',
+      new BRElement(), new BRElement(), new SpanElement()..text = '[',
+      new AnchorElement(
+        href: Uris.debugger(event.isolate))
+        ..text = 'debug',
+      new SpanElement()..text = ']'
+    ];
+  }
+
+  static List<Element> _managePauseExitEvent(M.PauseExitEvent event) {
+    return [
+      new SpanElement()..text = 'Isolate ',
+      new AnchorElement(
+        href: Uris.inspect(event.isolate))
+        ..text = event.isolate.name,
+      new SpanElement()..text = ' is paused at isolate exit',
+      new BRElement(), new BRElement(), new SpanElement()..text = '[',
+      new AnchorElement(
+        href: Uris.debugger(event.isolate))
+        ..text = 'debug',
+      new SpanElement()..text = ']'
+    ];
+  }
+
+  static List<Element> _managePauseBreakpointEvent(M.PauseBreakpointEvent event) {
+    String message = ' is paused';
+    if (event.breakpoint != null) {
+       message += ' at breakpoint ${event.breakpoint.number}';
+    }
+    return [
+      new SpanElement()..text = 'Isolate ',
+      new AnchorElement(
+        href: Uris.inspect(event.isolate))
+        ..text = event.isolate.name,
+      new SpanElement()
+        ..text = message,
+      new BRElement(), new BRElement(), new SpanElement()..text = '[',
+      new AnchorElement(
+        href: Uris.debugger(event.isolate))
+        ..text = 'debug',
+      new SpanElement()..text = ']'
+    ];
+  }
+
+  static List<Element> _managePauseInterruptedEvent(M.PauseInterruptedEvent event) {
+    return [
+      new SpanElement()..text = 'Isolate ',
+      new AnchorElement(
+        href: Uris.inspect(event.isolate))
+        ..text = event.isolate.name,
+      new SpanElement()
+        ..text = ' is paused',
+      new BRElement(), new BRElement(), new SpanElement()..text = '[',
+      new AnchorElement(
+        href: Uris.debugger(event.isolate))
+        ..text = 'debug',
+      new SpanElement()..text = ']'
+    ];
+  }
+
+  static List<Element> _managePauseExceptionEvent(M.PauseExceptionEvent event) {
+    return [
+      new SpanElement()..text = 'Isolate ',
+      new AnchorElement(
+        href: Uris.inspect(event.isolate))
+        ..text = event.isolate.name,
+      new SpanElement()
+        ..text = ' is paused due to exception',
+      new BRElement(), new BRElement(), new SpanElement()..text = '[',
+      new AnchorElement(
+        href: Uris.debugger(event.isolate))
+        ..text = 'debug',
+      new SpanElement()..text = ']'
+    ];
+  }
+
+  static List<Element> _manageNoneEvent(M.NoneEvent event) {
+    return [
+      new SpanElement()..text = 'Isolate ',
+      new AnchorElement(
+        href: Uris.inspect(event.isolate))
+        ..text = event.isolate.name,
+      new SpanElement()
+        ..text = ' is paused',
+      new BRElement(), new BRElement(), new SpanElement()..text = '[',
+      new AnchorElement(
+        href: Uris.debugger(event.isolate))
+        ..text = 'debug',
+      new SpanElement()..text = ']'
+    ];
+  }
+
+  static List<Element> _manageConnectionClosedEvent(M.ConnectionClosedEvent event) {
+    return [
+      new SpanElement()..text = 'Disconnected from VM: ${event.reason}',
+      new BRElement(), new BRElement(), new SpanElement()..text = '[',
+      new AnchorElement(href: Uris.vmConnect())..text = 'Connect to a VM',
+      new SpanElement()..text = ']'
+    ];
+  }
+
+  static List<Element> _manageInspectEvent(M.InspectEvent event) {
+    return [
+      new SpanElement()..text = 'Inspect ${event.inspectee.id}',
+      new BRElement(), new BRElement(), new SpanElement()..text = '[',
+      new AnchorElement(href: Uris.inspect(event.isolate,
+          object: event.inspectee))
+        ..text = 'Inspect',
+      new SpanElement()..text = ']'
+      // TODO(cbernaschina) add InstanceRefElement back.
+      //new InstanceRefElement()..instance = event.inspectee
+    ];
+  }
+
+  static List<Element> _manageIsolateReloadEvent(M.IsolateReloadEvent event) {
+    if (event.error != null) {
+      return [
+        new SpanElement()..text = 'Isolate reload failed:',
+        new BRElement(), new BRElement(),
+        new DivElement()
+          ..classes = ["indent", "error"]
+          ..text = event.error.message.toString()
+      ];
+    } else {
+      return [new SpanElement()..text = 'Isolate reload'];
+    }
+  }
+
+  EventDeleteEvent _toEvent(_) {
+    return new EventDeleteEvent(_event);
+  }
+
+  void _delete(EventDeleteEvent e) {
+    _onDelete.add(e);
+  }
+
+  void delete() {
+    _onDelete.add(new EventDeleteEvent(_event));
+  }
+}
diff --git a/runtime/observatory/lib/src/elements/nav/notify_exception.dart b/runtime/observatory/lib/src/elements/nav/notify_exception.dart
new file mode 100644
index 00000000000..cf0a4636f3b
--- /dev/null
+++ b/runtime/observatory/lib/src/elements/nav/notify_exception.dart
@@ -0,0 +1,128 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:html';
+import 'dart:async';
+import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
+import 'package:observatory/src/elements/helpers/tag.dart';
+import 'package:observatory/src/elements/helpers/uris.dart';
+import 'package:observatory/models.dart' show ConnectionException;
+
+
+class ExceptionDeleteEvent{
+  final Exception exception;
+  final StackTrace stacktrace;
+
+  ExceptionDeleteEvent(this.exception, {this.stacktrace});
+}
+
+class NavNotifyExceptionElement extends HtmlElement implements Renderable {
+  static const tag = const Tag<NavNotifyExceptionElement>('nav-exception');
+
+  RenderingScheduler _r;
+
+  Stream<RenderedEvent<NavNotifyExceptionElement>> get onRendered =>
+                                                                  _r.onRendered;
+
+  final StreamController<ExceptionDeleteEvent> _onDelete =
+      new StreamController<ExceptionDeleteEvent>.broadcast();
+  Stream<ExceptionDeleteEvent> get onDelete => _onDelete.stream;
+
+  Exception _exception;
+  StackTrace _stacktrace;
+  Exception get exception => _exception;
+  StackTrace get stacktrace => _stacktrace;
+
+  factory NavNotifyExceptionElement(Exception exception,
+      {StackTrace stacktrace: null, RenderingQueue queue}) {
+    assert(exception != null);
+    NavNotifyExceptionElement e = document.createElement(tag.name);
+    e._r = new RenderingScheduler(e, queue: queue);
+    e._exception = exception;
+    e._stacktrace = stacktrace;
+    return e;
+  }
+
+  NavNotifyExceptionElement.created() : super.created();
+
+  @override
+  void attached() {
+    super.attached();
+    _r.enable();
+  }
+
+  @override
+  void detached() {
+    super.detached();
+    children = [];
+    _r.disable(notify: true);
+  }
+
+  void render() {
+    if (exception is ConnectionException) {
+      renderConnectionException();
+    } else {
+      renderGenericException();
+    }
+  }
+
+  void renderConnectionException() {
+    children = [
+      new DivElement()
+        ..children = [
+        new SpanElement()..text = 'The request cannot be completed because the '
+                                  'VM is currently disconnected',
+        new BRElement(), new BRElement(),
+        new SpanElement()..text = '[',
+        new AnchorElement(href: Uris.vmConnect())
+          ..text = 'Connect to a different VM',
+        new SpanElement()..text = ']',
+        new ButtonElement()..innerHtml = '&times;'
+          ..onClick.map(_toEvent).listen(_delete)
+      ]
+    ];
+  }
+
+  void renderGenericException() {
+    List<Node> content;
+    content = [
+      new SpanElement()..text = 'Unexpected exception:',
+      new BRElement(), new BRElement(),
+      new DivElement()..text = exception.toString(),
+      new BRElement()
+    ];
+    if (stacktrace != null) {
+      content.addAll([
+        new SpanElement()..text = 'Stacktrace:',
+        new BRElement(), new BRElement(),
+        new DivElement()..text = stacktrace.toString(),
+        new BRElement()
+      ]);
+    }
+    content.addAll([
+      new SpanElement()..text = '[',
+      new AnchorElement(href: Uris.vmConnect())
+        ..text = 'Connect to a different VM',
+      new SpanElement()..text = ']',
+      new ButtonElement()..innerHtml = '&times;'
+        ..onClick.map(_toEvent).listen(_delete)
+    ]);
+    children = [
+      new DivElement()
+        ..children = content
+    ];
+  }
+
+  ExceptionDeleteEvent _toEvent(_) {
+    return new ExceptionDeleteEvent(exception, stacktrace: stacktrace);
+  }
+
+  void _delete(ExceptionDeleteEvent e) {
+    _onDelete.add(e);
+  }
+
+  void delete() {
+    _onDelete.add(new ExceptionDeleteEvent(exception, stacktrace: stacktrace));
+  }
+}
diff --git a/runtime/observatory/lib/src/elements/nav/notify_wrapper.dart b/runtime/observatory/lib/src/elements/nav/notify_wrapper.dart
new file mode 100644
index 00000000000..97f4ded559c
--- /dev/null
+++ b/runtime/observatory/lib/src/elements/nav/notify_wrapper.dart
@@ -0,0 +1,123 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:html';
+
+import 'package:observatory/app.dart';
+import 'package:observatory/repositories.dart';
+import 'package:observatory/src/elements/helpers/tag.dart';
+import 'package:observatory/src/elements/shims/binding.dart';
+import 'package:observatory/src/elements/nav/notify.dart';
+
+class NavNotifyElementWrapper extends HtmlElement {
+  static final binder = new Binder<NavNotifyElementWrapper>(
+    const [const Binding('notifications'), const Binding('notifyOnPause')]);
+
+  static const tag = const Tag<NavNotifyElementWrapper>('nav-notify');
+
+  NotificationRepository _notifications;
+  bool _notifyOnPause = true;
+  NotificationRepository get notifications => _notifications;
+  bool get notifyOnPause => _notifyOnPause;
+  set notifications(NotificationRepository value) {
+    _notifications = value; render();
+  }
+  set notifyOnPause(bool value) {
+    _notifyOnPause = value; render();
+  }
+
+  NavNotifyElementWrapper.created() : super.created() {
+    binder.registerCallback(this);
+    createShadowRoot();
+    render();
+  }
+
+  @override
+  void attached() {
+    super.attached();
+    render();
+  }
+
+  void render() {
+    shadowRoot.children = [];
+    if (_notifications == null) return;
+
+    shadowRoot.children = [
+      new StyleElement()
+        ..text = '''nav-notify-wrapped > div {
+          float: right;
+        }
+        nav-notify-wrapped > div > div {
+          display: block;
+          position: absolute;
+          top: 98%;
+          right: 0;
+          margin: 0;
+          padding: 0;
+          width: auto;
+          z-index: 1000;
+          background: none;
+        }
+
+        /* nav-exception & nav-event */
+
+        nav-exception > div, nav-event > div {
+          position: relative;
+          padding: 16px;
+          margin-top: 10px;
+          margin-right: 10px;
+          padding-right: 25px;
+          width: 500px;
+          color: #ddd;
+          background: rgba(0,0,0,.6);
+          border: solid 2px white;
+          box-shadow: 0 0 5px black;
+          border-radius: 5px;
+          animation: fadein 1s;
+        }
+
+        nav-exception *, nav-event * {
+          color: #ddd;
+          font-size: 12px;
+        }
+
+        nav-exception > div > a, nav-event > div > a {
+          color: white;
+          text-decoration: none;
+        }
+
+        nav-exception > div > a:hover, nav-event > div > a:hover {
+          text-decoration: underline;
+        }
+
+        nav-exception > div > div {
+          margin-left:20px;
+          white-space: pre
+        }
+
+        nav-exception > div > button, nav-event > div > button {
+          background: transparent;
+          border: none;
+          position: absolute;
+          display: block;
+          top: 4px;
+          right: 4px;
+          height: 18px;
+          width: 18px;
+          line-height: 16px;
+          border-radius: 9px;
+          color: white;
+          font-size: 18px;
+          cursor: pointer;
+          text-align: center;
+        }
+
+        nav-exception > div > button:hover, nav-event > div > button:hover {
+          background: rgba(255,255,255,0.5);
+        }''',
+      new NavNotifyElement(_notifications, notifyOnPause: notifyOnPause,
+                                 queue: ObservatoryApplication.app.queue)
+    ];
+  }
+}
diff --git a/runtime/observatory/lib/src/elements/nav_bar.dart b/runtime/observatory/lib/src/elements/nav_bar.dart
index e27bf9ee149..005a5d91d7d 100644
--- a/runtime/observatory/lib/src/elements/nav_bar.dart
+++ b/runtime/observatory/lib/src/elements/nav_bar.dart
@@ -4,10 +4,8 @@
 
 library nav_bar_element;
 
-import 'dart:html' hide Notification;
 import 'observatory_element.dart';
 import 'package:observatory/service.dart';
-import 'package:observatory/app.dart' show Notification;
 import 'package:polymer/polymer.dart';
 
 @CustomTag('library-nav-menu')
@@ -17,52 +15,3 @@ class LibraryNavMenuElement extends ObservatoryElement {
 
   LibraryNavMenuElement.created() : super.created();
 }
-
-@CustomTag('nav-notify')
-class NavNotifyElement extends ObservatoryElement {
-  @published ObservableList<Notification> notifications;
-  @published bool notifyOnPause = true;
-
-  NavNotifyElement.created() : super.created();
-}
-
-@CustomTag('nav-notify-event')
-class NavNotifyEventElement extends ObservatoryElement {
-  @published ObservableList<Notification> notifications;
-  @published Notification notification;
-  @published ServiceEvent event;
-  @published bool notifyOnPause = true;
-
-  void closeItem(MouseEvent e, var detail, Element target) {
-    notifications.remove(notification);
-  }
-
-  NavNotifyEventElement.created() : super.created();
-}
-
-@CustomTag('nav-notify-exception')
-class NavNotifyExceptionElement extends ObservatoryElement {
-  @published ObservableList<Notification> notifications;
-  @published Notification notification;
-  @published var exception;
-  @published var stacktrace;
-
-  exceptionChanged() {
-    notifyPropertyChange(#isNetworkError, true, false);
-    notifyPropertyChange(#isUnexpectedError, true, false);
-  }
-
-  @observable get isNetworkError {
-    return (exception is NetworkRpcException);
-  }
-
-  @observable get isUnexpectedError {
-    return (exception is! NetworkRpcException);
-  }
-
-  void closeItem(MouseEvent e, var detail, Element target) {
-    notifications.remove(notification);
-  }
-
-  NavNotifyExceptionElement.created() : super.created();
-}
diff --git a/runtime/observatory/lib/src/elements/nav_bar.html b/runtime/observatory/lib/src/elements/nav_bar.html
index d8c5c13a5dc..bf338840dce 100644
--- a/runtime/observatory/lib/src/elements/nav_bar.html
+++ b/runtime/observatory/lib/src/elements/nav_bar.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="action_link.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="library-nav-menu" extends="observatory-element">
+
+<polymer-element name="library-nav-menu">
   <template>
     <nav-menu link="{{ makeLink('/inspect', library) }}"
               anchor="{{ library.name }}" last="{{ last }}">
@@ -11,251 +11,4 @@
   </template>
 </polymer-element>
 
-<polymer-element name="nav-notify" extends="observatory-element">
-  <template>
-    <style>
-      .menu {
-        float: right;
-      }
-      .menu .list {
-        display: block;
-        position: absolute;
-        top: 98%;
-        right: 0;
-        margin: 0;
-        padding: 0;
-        width: auto;
-        z-index: 1000;
-        font: 400 12px 'Montserrat', sans-serif;
-        color: white;
-        background: none;
-      }
-    </style>
-
-    <div class="menu">
-      <div class="list">
-        <template repeat="{{ notification in notifications }}">
-          <template if="{{ notification.event != null }}">
-            <nav-notify-event notifications="{{ notifications }}"
-                              notification="{{ notification }}"
-                              event="{{ notification.event }}"
-                              notifyOnPause="{{ notifyOnPause }}">
-            </nav-notify-event>
-          </template>
-          <template if="{{ notification.exception != null }}">
-            <nav-notify-exception notifications="{{ notifications }}"
-                              notification="{{ notification }}"
-                              exception="{{ notification.exception }}"
-                              stacktrace="{{ notification.stacktrace }}">
-            </nav-notify-exception>
-          </template>
-        </template>
-      </div>
-    </div>
-  </template>
-</polymer-element>
-
-<polymer-element name="nav-notify-event" extends="observatory-element">
-  <template>
-    <style>
-      .item {
-        position: relative;
-        padding: 16px;
-        margin-top: 10px;
-        margin-right: 10px;
-        padding-right: 25px;
-        width: 250px;
-        color: #ddd;
-        background: rgba(0,0,0,.6);
-        border: solid 2px white;
-        box-shadow: 0 0 5px black;
-        border-radius: 5px;
-        animation: fadein 1s;
-      }
-
-      .wide-item {
-        width: 50vw;
-      }
-
-      @keyframes fadein {
-        from { opacity: 0; }
-        to   { opacity: 1; }
-      }
-
-      a.link {
-        color: white;
-        text-decoration: none;
-      }
-      a.link:hover {
-        text-decoration: underline;
-      }
-
-      a.boxclose {
-        position: absolute;
-        display: block;
-        top: 4px;
-        right: 4px;
-        height: 18px;
-        width: 18px;
-        line-height: 16px;
-        border-radius: 9px;
-        color: white;
-        font-size: 18px;
-        cursor: pointer;
-        text-align: center;
-      }
-      a.boxclose:hover {
-        background: rgba(255,255,255,0.5);
-      }
-      .error {
-        white-space: pre;
-      }
-    </style>
-    <template if="{{ event != null }}">
-      <template if="{{ notifyOnPause && event.isPauseEvent }}">
-        <div class="item">
-          Isolate
-          <a class="link" on-click="{{ goto }}"
-             _href="{{ gotoLink('/inspect', event.isolate) }}">{{ event.isolate.name }}</a>
-          is paused
-          <template if="{{ event.kind == 'PauseStart' }}">
-            at isolate start
-          </template>
-          <template if="{{ event.kind == 'PauseExit' }}">
-            at isolate exit
-          </template>
-          <template if="{{ event.breakpoint != null }}">
-            at breakpoint {{ event.breakpoint.number }}
-          </template>
-          <template if="{{ event.kind == 'PauseException' }}">
-            due to exception
-          </template>
-
-          <br><br>
-          [<a class="link" on-click="{{ goto }}"
-              _href="{{ gotoLink('/debugger', event.isolate) }}">debug</a>]
-
-          <a class="boxclose" on-click="{{ closeItem }}">&times;</a>
-        </div>
-      </template>
-      <template if="{{ event.kind == 'ConnectionClosed' }}">
-        <div class="item">
-          Disconnected from VM: {{ event.reason }}
-          <br><br>
-          [<a class="link" on-click="{{ goto }}"
-              _href="{{ gotoLink('/vm-connect') }}">Connect to a VM</a>]
-          <a class="boxclose" on-click="{{ closeItem }}">&times;</a>
-        </div>
-      </template>
-      <template if="{{ event.kind == 'Inspect' }}">
-        <div class="item">
-          Inspect <any-service-ref ref="{{ event.inspectee }}"></any-service-ref>
-          <br><br>
-          <a class="boxclose" on-click="{{ closeItem }}">&times;</a>
-        </div>
-      </template>
-      <template if="{{ event.kind == 'IsolateReload' }}">
-        <div class="wide-item item">
-          Isolate reload
-          <template if="{{ event.reloadError != null }}">
-            failed:
-            <br>
-            <br>
-            <div class="indent error">{{ event.reloadError.message.toString() }}</div><br>
-          </template>
-          <template if="{{ event.reloadError == null }}">
-            succeeded
-          </template>
-          <a class="boxclose" on-click="{{ closeItem }}">&times;</a>
-        </div>
-      </template>
-    </template>
-  </template>
-</polymer-element>
-
-
-<polymer-element name="nav-notify-exception" extends="observatory-element">
-  <template>
-    <style>
-      .item {
-        position: relative;
-        padding: 16px;
-        margin-top: 10px;
-        margin-right: 10px;
-        padding-right: 25px;
-        width: 500px;
-        color: #ddd;
-        background: rgba(0,0,0,.6);
-        border: solid 2px white;
-        box-shadow: 0 0 5px black;
-        border-radius: 5px;
-        animation: fadein 1s;
-      }
-
-      @keyframes fadein {
-        from { opacity: 0; }
-        to   { opacity: 1; }
-      }
-
-      a.link {
-        color: white;
-        text-decoration: none;
-      }
-      a.link:hover {
-        text-decoration: underline;
-      }
-      .indent {
-        margin-left:20px;
-      }
-
-      a.boxclose {
-        position: absolute;
-        display: block;
-        top: 4px;
-        right: 4px;
-        height: 18px;
-        width: 18px;
-        line-height: 16px;
-        border-radius: 9px;
-        color: white;
-        font-size: 18px;
-        cursor: pointer;
-        text-align: center;
-      }
-      a.boxclose:hover {
-        background: rgba(255,255,255,0.5);
-      }
-      .stacktrace {
-        white-space: pre
-      }
-    </style>
-    <template if="{{ isUnexpectedError }}">
-      <!-- TODO(turnidge): Add a file-a-bug link to this notification -->
-      <div class="item">
-        Unexpected exception:<br><br>
-        <div class="indent">{{ exception.toString() }}</div><br>
-        <template if="{{ stacktrace != null }}">
-          Stacktrace:<br><br>
-          <div class="indent stacktrace">{{ stacktrace.toString() }}</div>
-          <br>
-        </template>
-        [<a class="link" on-click="{{ goto }}"
-            _href="{{ gotoLink('vm-connect') }}">Connect to a different VM</a>]
-        <a class="boxclose" on-click="{{ closeItem }}">&times;</a>
-    </div>
-    </template>
-    <template if="{{ isNetworkError }}">
-      <div class="item">
-        The request cannot be completed because the VM is currently
-        disconnected.
-        <br><br>
-        [<a class="link" on-click="{{ goto }}"
-            _href="{{ gotoLink('vm-connect') }}">Connect to a different VM</a>]
-        <a class="boxclose" on-click="{{ closeItem }}">&times;</a>
-    </div>
-    </template>
-  </template>
-</polymer-element>
-
-
 <script type="application/dart" src="nav_bar.dart"></script>
diff --git a/runtime/observatory/lib/src/elements/object_common.html b/runtime/observatory/lib/src/elements/object_common.html
index 14311e072e2..a41b8283e63 100644
--- a/runtime/observatory/lib/src/elements/object_common.html
+++ b/runtime/observatory/lib/src/elements/object_common.html
@@ -5,11 +5,11 @@
 <link rel="import" href="function_ref.html">
 <link rel="import" href="inbound_reference.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="eval_link.html">
 
-<polymer-element name="object-common" extends="observatory-element">
+<polymer-element name="object-common">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <div class="memberList">
diff --git a/runtime/observatory/lib/src/elements/object_view.html b/runtime/observatory/lib/src/elements/object_view.html
index c512b00d97e..c612258f311 100644
--- a/runtime/observatory/lib/src/elements/object_view.html
+++ b/runtime/observatory/lib/src/elements/object_view.html
@@ -5,12 +5,12 @@
 <link rel="import" href="function_ref.html">
 <link rel="import" href="inbound_reference.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="object_common.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="eval_link.html">
 
-<polymer-element name="object-view" extends="observatory-element">
+<polymer-element name="object-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/objectpool_view.html b/runtime/observatory/lib/src/elements/objectpool_view.html
index 0e158b83d34..82dad68bd41 100644
--- a/runtime/observatory/lib/src/elements/objectpool_view.html
+++ b/runtime/observatory/lib/src/elements/objectpool_view.html
@@ -5,12 +5,12 @@
 <link rel="import" href="function_ref.html">
 <link rel="import" href="inbound_reference.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="object_common.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="eval_link.html">
 
-<polymer-element name="objectpool-view" extends="observatory-element">
+<polymer-element name="objectpool-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/objectstore_view.html b/runtime/observatory/lib/src/elements/objectstore_view.html
index 8988fceff53..2fbe56b5736 100644
--- a/runtime/observatory/lib/src/elements/objectstore_view.html
+++ b/runtime/observatory/lib/src/elements/objectstore_view.html
@@ -4,12 +4,12 @@
 <link rel="import" href="field_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="instance_ref.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="library_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="script_ref.html">
 
-<polymer-element name="objectstore-view" extends="observatory-element">
+<polymer-element name="objectstore-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
diff --git a/runtime/observatory/lib/src/elements/observatory_application.html b/runtime/observatory/lib/src/elements/observatory_application.html
index 73a2615e8b8..d91819f0d4b 100644
--- a/runtime/observatory/lib/src/elements/observatory_application.html
+++ b/runtime/observatory/lib/src/elements/observatory_application.html
@@ -1,7 +1,7 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_view.html">
-<polymer-element name="observatory-application" extends="observatory-element">
+<polymer-element name="observatory-application">
   <!-- This element explicitly manages its child elements -->
 </polymer-element>
 
diff --git a/runtime/observatory/lib/src/elements/observatory_element.dart b/runtime/observatory/lib/src/elements/observatory_element.dart
index 164f0798713..a661ccfc2fd 100644
--- a/runtime/observatory/lib/src/elements/observatory_element.dart
+++ b/runtime/observatory/lib/src/elements/observatory_element.dart
@@ -11,7 +11,6 @@ import 'package:observatory/service.dart';
 import 'package:polymer/polymer.dart';
 
 /// Base class for all Observatory custom elements.
-@CustomTag('observatory-element')
 class ObservatoryElement extends PolymerElement {
   ObservatoryElement.created() : super.created();
 
diff --git a/runtime/observatory/lib/src/elements/observatory_element.html b/runtime/observatory/lib/src/elements/observatory_element.html
deleted file mode 100644
index dce89dcdda8..00000000000
--- a/runtime/observatory/lib/src/elements/observatory_element.html
+++ /dev/null
@@ -1,6 +0,0 @@
-<link rel="import" href="../../../../packages/polymer/polymer.html">
-
-<polymer-element name="observatory-element">
-</polymer-element>
-
-<script type="application/dart" src="observatory_element.dart"></script>
\ No newline at end of file
diff --git a/runtime/observatory/lib/src/elements/persistent_handles.html b/runtime/observatory/lib/src/elements/persistent_handles.html
index 4f10661891a..612df33f47a 100644
--- a/runtime/observatory/lib/src/elements/persistent_handles.html
+++ b/runtime/observatory/lib/src/elements/persistent_handles.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="persistent-handles-page" extends="observatory-element">
+
+<polymer-element name="persistent-handles-page">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/ports.html b/runtime/observatory/lib/src/elements/ports.html
index 4d3f7ac78c4..37b9e857450 100644
--- a/runtime/observatory/lib/src/elements/ports.html
+++ b/runtime/observatory/lib/src/elements/ports.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="ports-page" extends="observatory-element">
+
+<polymer-element name="ports-page">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/script_inset.html b/runtime/observatory/lib/src/elements/script_inset.html
index dd211557edf..c8ea9df2dd7 100644
--- a/runtime/observatory/lib/src/elements/script_inset.html
+++ b/runtime/observatory/lib/src/elements/script_inset.html
@@ -1,5 +1,5 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
+
 
 <polymer-element name="icon-refresh" noscript>
   <template>
@@ -27,7 +27,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="script-inset" extends="observatory-element">
+<polymer-element name="script-inset">
   <template>
     <style>
       a {
diff --git a/runtime/observatory/lib/src/elements/script_ref.html b/runtime/observatory/lib/src/elements/script_ref.html
index ccbb17732f8..7a9f0f1d5d9 100644
--- a/runtime/observatory/lib/src/elements/script_ref.html
+++ b/runtime/observatory/lib/src/elements/script_ref.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="script-ref" extends="service-ref">
+<polymer-element name="script-ref">
 <template>
   <link rel="stylesheet" href="css/shared.css">
   <a on-click="{{ goto }}" title="{{ hoverText }}" _href="{{ url }}">{{ name }}</a>
diff --git a/runtime/observatory/lib/src/elements/script_view.html b/runtime/observatory/lib/src/elements/script_view.html
index 28580369462..fc0a86951d5 100644
--- a/runtime/observatory/lib/src/elements/script_view.html
+++ b/runtime/observatory/lib/src/elements/script_view.html
@@ -1,9 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="script_inset.html">
 
-<polymer-element name="script-view" extends="observatory-element">
+<polymer-element name="script-view">
 <template>
   <link rel="stylesheet" href="css/shared.css">
   <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/service_ref.dart b/runtime/observatory/lib/src/elements/service_ref.dart
index e9aad6d73d7..d368713f5f0 100644
--- a/runtime/observatory/lib/src/elements/service_ref.dart
+++ b/runtime/observatory/lib/src/elements/service_ref.dart
@@ -14,7 +14,6 @@ import 'class_ref.dart';
 import 'library_ref.dart';
 import 'observatory_element.dart';
 
-@CustomTag('service-ref')
 class ServiceRefElement extends ObservatoryElement {
   @published ServiceObject ref;
   @published bool internal = false;
diff --git a/runtime/observatory/lib/src/elements/service_ref.html b/runtime/observatory/lib/src/elements/service_ref.html
index 17ce4c52f5f..c6e8b8b7796 100644
--- a/runtime/observatory/lib/src/elements/service_ref.html
+++ b/runtime/observatory/lib/src/elements/service_ref.html
@@ -1,13 +1,9 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="service-ref" extends="observatory-element">
+<polymer-element name="any-service-ref">
 </polymer-element>
 
-<polymer-element name="any-service-ref" extends="observatory-element">
-</polymer-element>
-
-<polymer-element name="object-ref" extends="service-ref">
+<polymer-element name="object-ref">
   <template><link rel="stylesheet" href="css/shared.css">
 
     <template if="{{ ref.isObjectPool }}">
diff --git a/runtime/observatory/lib/src/elements/service_view.html b/runtime/observatory/lib/src/elements/service_view.html
index 3d8c76e4517..3ddbbe45ec9 100644
--- a/runtime/observatory/lib/src/elements/service_view.html
+++ b/runtime/observatory/lib/src/elements/service_view.html
@@ -11,15 +11,15 @@
 <link rel="import" href="instance_view.html">
 <link rel="import" href="library_view.html">
 <link rel="import" href="heap_snapshot.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="script_view.html">
 <link rel="import" href="vm_view.html">
-<polymer-element name="service-view" extends="observatory-element">
+<polymer-element name="service-view">
   <!-- This element explicitly manages the child elements to avoid setting
        an observable property on the old element to an invalid type. -->
 </polymer-element>
 
-<polymer-element name="trace-view" extends="observatory-element">
+<polymer-element name="trace-view">
    <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -47,7 +47,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="map-viewer" extends="observatory-element">
+<polymer-element name="map-viewer">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
@@ -79,7 +79,7 @@
   </template>
 </polymer-element>
 
-<polymer-element name="list-viewer" extends="observatory-element">
+<polymer-element name="list-viewer">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
diff --git a/runtime/observatory/lib/src/elements/timeline_page.html b/runtime/observatory/lib/src/elements/timeline_page.html
index 40c161b062a..881c7ed59e3 100644
--- a/runtime/observatory/lib/src/elements/timeline_page.html
+++ b/runtime/observatory/lib/src/elements/timeline_page.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="timeline-page" extends="observatory-element">
+
+<polymer-element name="timeline-page">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
diff --git a/runtime/observatory/lib/src/elements/vm_connect.html b/runtime/observatory/lib/src/elements/vm_connect.html
index 9af365e7376..d95b6ba8ae5 100644
--- a/runtime/observatory/lib/src/elements/vm_connect.html
+++ b/runtime/observatory/lib/src/elements/vm_connect.html
@@ -1,8 +1,8 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
 
-<polymer-element name="vm-connect" extends="observatory-element">
+
+<polymer-element name="vm-connect">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
diff --git a/runtime/observatory/lib/src/elements/vm_ref.html b/runtime/observatory/lib/src/elements/vm_ref.html
index e7cb8e4a46f..3166ac46567 100644
--- a/runtime/observatory/lib/src/elements/vm_ref.html
+++ b/runtime/observatory/lib/src/elements/vm_ref.html
@@ -1,7 +1,7 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="service_ref.html">
 
-<polymer-element name="vm-ref" extends="service-ref">
+<polymer-element name="vm-ref">
   <template><link rel="stylesheet" href="css/shared.css">
     <a on-click="{{ goto }}" _href="{{ url }}">{{ ref.name }}</a>
   </template>
diff --git a/runtime/observatory/lib/src/elements/vm_view.html b/runtime/observatory/lib/src/elements/vm_view.html
index dfa37050597..d4a29c0e42e 100644
--- a/runtime/observatory/lib/src/elements/vm_view.html
+++ b/runtime/observatory/lib/src/elements/vm_view.html
@@ -4,10 +4,10 @@
 <link rel="import" href="isolate_summary.html">
 <link rel="import" href="library_ref.html">
 <link rel="import" href="nav_bar.html">
-<link rel="import" href="observatory_element.html">
+
 <link rel="import" href="script_ref.html">
 
-<polymer-element name="vm-view" extends="observatory-element">
+<polymer-element name="vm-view">
   <template>
     <link rel="stylesheet" href="css/shared.css">
 
diff --git a/runtime/observatory/lib/src/mocks/exceptions/connection_exception.dart b/runtime/observatory/lib/src/mocks/exceptions/connection_exception.dart
new file mode 100644
index 00000000000..127cb20833f
--- /dev/null
+++ b/runtime/observatory/lib/src/mocks/exceptions/connection_exception.dart
@@ -0,0 +1,10 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of mocks;
+
+class ConnectionExceptionMock implements M.ConnectionException {
+  final String message;
+  const ConnectionExceptionMock({this.message});
+}
diff --git a/runtime/observatory/lib/src/mocks/objects/error.dart b/runtime/observatory/lib/src/mocks/objects/error.dart
new file mode 100644
index 00000000000..8b47830341c
--- /dev/null
+++ b/runtime/observatory/lib/src/mocks/objects/error.dart
@@ -0,0 +1,20 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of mocks;
+
+class ErrorRefMock implements M.ErrorRef {
+  final String id;
+  final M.ErrorKind kind;
+  final String message;
+  const ErrorRefMock({this.id, this.kind, this.message});
+}
+
+class ErrorMock implements M.Error {
+  final String id;
+  final M.ErrorKind kind;
+  final String message;
+  final int size;
+  const ErrorMock({this.id, this.kind, this.message, this.size});
+}
diff --git a/runtime/observatory/lib/src/mocks/objects/event.dart b/runtime/observatory/lib/src/mocks/objects/event.dart
index d4c8eea4ddc..6a646f3cdb5 100644
--- a/runtime/observatory/lib/src/mocks/objects/event.dart
+++ b/runtime/observatory/lib/src/mocks/objects/event.dart
@@ -6,11 +6,137 @@ part of mocks;
 
 class VMUpdateEventMock implements M.VMUpdateEvent {
   final M.VMRef vm;
-  const VMUpdateEventMock({this.vm});
+  final DateTime timestamp;
+  const VMUpdateEventMock({this.timestamp, this.vm});
+}
+class IsolateStartEventMock implements M.IsolateStartEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  const IsolateStartEventMock({this.timestamp, this.isolate});
+}
+class IsolateRunnableEventMock implements M.IsolateRunnableEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  const IsolateRunnableEventMock({this.timestamp, this.isolate});
+}
+class IsolateExitEventMock implements M.IsolateExitEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  const IsolateExitEventMock({this.timestamp, this.isolate});
 }
-
 class IsolateUpdateEventMock implements M.IsolateUpdateEvent {
   final DateTime timestamp;
   final M.IsolateRef isolate;
   const IsolateUpdateEventMock({this.timestamp, this.isolate});
 }
+class IsolateRealodEventMock implements M.IsolateReloadEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final M.Error error;
+  const IsolateRealodEventMock({this.timestamp, this.isolate, this.error});
+}
+class ServiceExtensionAddedEventMock implements M.ServiceExtensionAddedEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final String extensionRPC;
+  const ServiceExtensionAddedEventMock({this.extensionRPC, this.isolate,
+      this.timestamp});
+}
+class PauseStartEventMock implements M.PauseStartEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  const PauseStartEventMock({this.isolate, this.timestamp});
+}
+class PauseExitEventMock implements M.PauseExitEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  const PauseExitEventMock({this.isolate, this.timestamp});
+}
+class PauseBreakpointEventMock implements M.PauseBreakpointEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final M.Breakpoint breakpoint;
+  final List<M.Breakpoint> pauseBreakpoints;
+  final M.Frame topFrame;
+  final bool atAsyncSuspension;
+  const PauseBreakpointEventMock({this.timestamp, this.isolate, this.breakpoint,
+      this.pauseBreakpoints, this.topFrame, this.atAsyncSuspension});
+}
+class PauseInterruptedEventMock implements M.PauseInterruptedEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final M.Frame topFrame;
+  final bool atAsyncSuspension;
+  const PauseInterruptedEventMock({this.timestamp, this.isolate, this.topFrame,
+      this.atAsyncSuspension});
+}
+class PauseExceptionEventMock implements M.PauseExceptionEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final M.Frame topFrame;
+  final M.InstanceRef exception;
+  const PauseExceptionEventMock({this.timestamp, this.isolate, this.topFrame,
+      this.exception});
+}
+class ResumeEventMock implements M.ResumeEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  const ResumeEventMock({this.timestamp, this.isolate});
+}
+class BreakpointAddedEventMock implements M.BreakpointAddedEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final M.Breakpoint breakpoint;
+  const BreakpointAddedEventMock({this.timestamp, this.isolate,
+      this.breakpoint});
+}
+class BreakpointResolvedEventMock implements M.BreakpointResolvedEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final M.Breakpoint breakpoint;
+  const BreakpointResolvedEventMock({this.timestamp, this.isolate,
+      this.breakpoint});
+}
+class BreakpointRemovedEventMock implements M.BreakpointRemovedEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final M.Breakpoint breakpoint;
+  const BreakpointRemovedEventMock({this.timestamp, this.isolate,
+      this.breakpoint});
+}
+class InspectEventMock implements M.InspectEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final M.InstanceRef inspectee;
+  const InspectEventMock({this.timestamp, this.isolate, this.inspectee});
+}
+class NoneEventMock implements M.NoneEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  const NoneEventMock({this.timestamp, this.isolate});
+}
+class GCEventMock implements M.GCEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  const GCEventMock({this.timestamp, this.isolate});
+}
+class ExtensionEventMock implements M.ExtensionEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final String extensionKind;
+  final M.ExtensionData extensionData;
+  const ExtensionEventMock({this.timestamp, this.isolate, this.extensionKind,
+      this.extensionData});
+}
+class TimelineEventsEventMock implements M.TimelineEventsEvent {
+  final DateTime timestamp;
+  final M.IsolateRef isolate;
+  final List<M.TimelineEvent> timelineEvents;
+  const TimelineEventsEventMock({this.timestamp, this.isolate,
+      this.timelineEvents});
+}
+class ConnectionClockedEventMock implements M.ConnectionClosedEvent {
+  final DateTime timestamp;
+  final String reason;
+  const ConnectionClockedEventMock({this.timestamp, this.reason});
+}
diff --git a/runtime/observatory/lib/src/mocks/objects/notification.dart b/runtime/observatory/lib/src/mocks/objects/notification.dart
new file mode 100644
index 00000000000..68bfd75d020
--- /dev/null
+++ b/runtime/observatory/lib/src/mocks/objects/notification.dart
@@ -0,0 +1,16 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of mocks;
+
+class ExceptionNotificationMock implements M.ExceptionNotification {
+  final Exception exception;
+  final StackTrace stacktrace;
+  const ExceptionNotificationMock({this.exception, this.stacktrace});
+}
+
+class EventNotificationMock implements M.EventNotification {
+  final M.Event event;
+  const EventNotificationMock({this.event});
+}
diff --git a/runtime/observatory/lib/src/mocks/objects/script.dart b/runtime/observatory/lib/src/mocks/objects/script.dart
new file mode 100644
index 00000000000..bb264dc32fa
--- /dev/null
+++ b/runtime/observatory/lib/src/mocks/objects/script.dart
@@ -0,0 +1,31 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of mocks;
+
+class ScriptRefMock implements M.ScriptRef {
+  final String id;
+  final String uri;
+  const ScriptRefMock({this.id, this.uri});
+}
+
+typedef int TokenToInt(int token);
+
+class ScriptMock implements M.Script {
+  final String id;
+  final int size;
+  final String uri;
+  final String source;
+
+  final TokenToInt _tokenToLine;
+  final TokenToInt _tokenToCol;
+
+  int tokenToLine(int token) => _tokenToLine(token);
+  int tokenToCol(int token) => _tokenToCol(token);
+
+  const ScriptMock({this.id, this.size, this.uri, this.source,
+      TokenToInt tokenToLine, TokenToInt tokenToCol})
+    : _tokenToLine = tokenToLine,
+      _tokenToCol = tokenToCol;
+}
diff --git a/runtime/observatory/lib/src/mocks/objects/source_location.dart b/runtime/observatory/lib/src/mocks/objects/source_location.dart
new file mode 100644
index 00000000000..481b44b8770
--- /dev/null
+++ b/runtime/observatory/lib/src/mocks/objects/source_location.dart
@@ -0,0 +1,12 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of mocks;
+
+class SourceLocationMock implements M.SourceLocation {
+  final M.ScriptRef script;
+  final int tokenPos;
+  final int endTokenPos;
+  const SourceLocationMock({this.script, this.tokenPos, this.endTokenPos});
+}
diff --git a/runtime/observatory/lib/src/mocks/repositories/notification.dart b/runtime/observatory/lib/src/mocks/repositories/notification.dart
new file mode 100644
index 00000000000..cf7f2b9e433
--- /dev/null
+++ b/runtime/observatory/lib/src/mocks/repositories/notification.dart
@@ -0,0 +1,58 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of mocks;
+
+class NotificationChangeEventMock implements M.NotificationChangeEvent {
+  final NotificationRepositoryMock repository;
+  const NotificationChangeEventMock({this.repository});
+}
+
+typedef void NotificationRepositoryMockCallback(M.Notification notification);
+
+class NotificationRepositoryMock implements M.NotificationRepository {
+  final StreamController<M.NotificationChangeEvent> _onChange =
+      new StreamController<M.NotificationChangeEvent>.broadcast();
+  Stream<M.NotificationChangeEvent> get onChange => _onChange.stream;
+
+  bool get hasListeners => _onChange.hasListener;
+
+  final Iterable<M.Notification> _list;
+  final NotificationRepositoryMockCallback _add;
+  final NotificationRepositoryMockCallback _delete;
+
+  bool addInvoked = false;
+  bool listInvoked = false;
+  bool deleteInvoked = false;
+  bool deleteAllInvoked = false;
+
+
+  void add(M.Notification notification) {
+    addInvoked = true;
+    if (_add != null) _add(notification);
+  }
+
+  Iterable<M.Notification> list() {
+    listInvoked = true;
+    return _list;
+  }
+
+  void delete(M.Notification notification) {
+    deleteInvoked = true;
+    if (_add != null) _delete(notification);
+  }
+
+  void deleteAll() { deleteAllInvoked = true; }
+
+  void triggerChangeEvent() {
+    _onChange.add(new NotificationChangeEventMock(repository: this));
+  }
+
+  NotificationRepositoryMock({Iterable<M.Notification> list : const [],
+      NotificationRepositoryMockCallback add,
+      NotificationRepositoryMockCallback delete})
+    : _list = list,
+      _add = add,
+      _delete = delete;
+}
diff --git a/runtime/observatory/lib/src/models/exceptions.dart b/runtime/observatory/lib/src/models/exceptions.dart
new file mode 100644
index 00000000000..871c0955474
--- /dev/null
+++ b/runtime/observatory/lib/src/models/exceptions.dart
@@ -0,0 +1,49 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class BasicException implements Exception {
+  String get message;
+}
+
+abstract class ConnectionException implements BasicException {}
+
+abstract class ResponseException implements BasicException {}
+
+abstract class RequestException implements BasicException {}
+
+abstract class ParseErrorException implements RequestException {}
+
+abstract class InvalidRequestException implements RequestException {}
+
+abstract class MethodNotFoundException implements RequestException {}
+
+abstract class InvalidParamsException implements RequestException {}
+
+abstract class InternalErrorException implements RequestException {}
+
+abstract class FeatureDisabledException implements RequestException {}
+
+abstract class CannotAddBreakpointException implements RequestException {}
+
+abstract class StreamAlreadySubscribedException implements RequestException {}
+
+abstract class StreamNotSubscribedException implements RequestException {}
+
+abstract class IsolateMustBeRunnableException implements RequestException {}
+
+abstract class IsolateMustBePausedException implements RequestException {}
+
+abstract class IsolateIsReloadingException implements RequestException {}
+
+abstract class FileSystemAlreadyExistsException implements RequestException {}
+
+abstract class FileSystemDoesNotExistException implements RequestException {}
+
+abstract class FileDoesNotExistException implements RequestException {}
+
+abstract class IsolateReloadFailedException implements RequestException {}
+
+abstract class UnknownException implements RequestException {}
diff --git a/runtime/observatory/lib/src/models/objects/breakpoint.dart b/runtime/observatory/lib/src/models/objects/breakpoint.dart
new file mode 100644
index 00000000000..e5e9324aad9
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/breakpoint.dart
@@ -0,0 +1,13 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class Breakpoint extends Object {
+  /// A number identifying this breakpoint to the user.
+  int get number;
+
+  /// Has this breakpoint been assigned to a specific program location?
+  bool get resolved;
+}
diff --git a/runtime/observatory/lib/src/models/objects/class.dart b/runtime/observatory/lib/src/models/objects/class.dart
index ed23902102c..a2a90077f16 100644
--- a/runtime/observatory/lib/src/models/objects/class.dart
+++ b/runtime/observatory/lib/src/models/objects/class.dart
@@ -12,7 +12,7 @@ abstract class ClassRef extends ObjectRef {
 abstract class Class extends ObjectRef implements ClassRef {
   /// The error which occurred during class finalization, if it exists.
   /// [optional]
-  //ErrorRef get error;
+  ErrorRef get error;
 
   /// Is this an abstract class?
   bool get isAbstract;
@@ -21,10 +21,10 @@ abstract class Class extends ObjectRef implements ClassRef {
   bool get isConst;
 
   /// The library which contains this class.
-  //LibraryRef get library;
+  LibraryRef get library;
 
   /// The location of this class in the source code.[optional]
-  //SourceLocation get location;
+  SourceLocation get location;
 
   /// The superclass of this class, if any. [optional]
   ClassRef get superclass;
@@ -32,17 +32,17 @@ abstract class Class extends ObjectRef implements ClassRef {
   /// The supertype for this class, if any.
   ///
   /// The value will be of the kind: Type. [optional]
-  //InstanceRef get superType;
+  InstanceRef get superType;
 
   /// A list of interface types for this class.
   ///
   /// The values will be of the kind: Type.
-  //Iterable<InstanceRef> get interfaces;
+  Iterable<InstanceRef> get interfaces;
 
   /// The mixin type for this class, if any.
   ///
   /// The value will be of the kind: Type. [optional]
-  //Iterable<InstanceRef> get mixin;
+  Iterable<InstanceRef> get mixin;
 
   /// A list of fields in this class. Does not include fields from
   /// superclasses.
diff --git a/runtime/observatory/lib/src/models/objects/error.dart b/runtime/observatory/lib/src/models/objects/error.dart
new file mode 100644
index 00000000000..b5d1bbd3b29
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/error.dart
@@ -0,0 +1,27 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+enum ErrorKind {
+  /// The isolate has encountered an unhandled Dart exception.
+  UnhandledException,
+  /// The isolate has encountered a Dart language error in the program.
+  LanguageError,
+  /// The isolate has encounted an internal error. These errors should be
+  /// reported as bugs.
+  InternalError,
+  /// The isolate has been terminated by an external source.
+  TerminationError
+}
+
+abstract class ErrorRef extends ObjectRef {
+  String get id;
+  ErrorKind get kind;
+  String get message;
+}
+
+abstract class Error extends Object implements ErrorRef {
+
+}
diff --git a/runtime/observatory/lib/src/models/objects/event.dart b/runtime/observatory/lib/src/models/objects/event.dart
index 732f574800f..aff194695c4 100644
--- a/runtime/observatory/lib/src/models/objects/event.dart
+++ b/runtime/observatory/lib/src/models/objects/event.dart
@@ -4,10 +4,72 @@
 
 part of models;
 
-abstract class VMUpdateEvent {
+abstract class Event {
+  DateTime get timestamp;
+  static bool isPauseEvent(Event event) {
+    return event is PauseStartEvent || event is PauseExitEvent ||
+        event is PauseBreakpointEvent || event is PauseInterruptedEvent ||
+        event is PauseExceptionEvent || event is NoneEvent;
+  }
+}
+abstract class VMEvent extends Event {
   VMRef get vm;
 }
-
-abstract class IsolateUpdateEvent {
+abstract class VMUpdateEvent extends VMEvent {}
+abstract class IsolateEvent extends Event {
   IsolateRef get isolate;
 }
+abstract class IsolateStartEvent extends IsolateEvent {}
+abstract class IsolateRunnableEvent extends IsolateEvent {}
+abstract class IsolateExitEvent extends IsolateEvent {}
+abstract class IsolateUpdateEvent extends IsolateEvent {}
+abstract class IsolateReloadEvent extends IsolateEvent {
+  ErrorRef get error;
+}
+abstract class ServiceExtensionAddedEvent extends IsolateEvent {
+  String get extensionRPC;
+}
+abstract class DebugEvent extends IsolateEvent {}
+abstract class PauseStartEvent extends DebugEvent {}
+abstract class PauseExitEvent extends DebugEvent {}
+abstract class PauseBreakpointEvent extends DebugEvent {
+  /// [optional]
+  Breakpoint get breakpoint;
+  Iterable<Breakpoint> get pauseBreakpoints;
+  Frame get topFrame;
+  bool get atAsyncSuspension;
+}
+abstract class PauseInterruptedEvent extends DebugEvent {
+  Frame get topFrame;
+  bool get atAsyncSuspension;
+}
+abstract class PauseExceptionEvent extends DebugEvent {
+  Frame get topFrame;
+  InstanceRef get exception;
+}
+abstract class ResumeEvent extends DebugEvent {}
+abstract class BreakpointAddedEvent extends DebugEvent {
+  Breakpoint get breakpoint;
+}
+abstract class BreakpointResolvedEvent extends DebugEvent {
+  Breakpoint get breakpoint;
+}
+abstract class BreakpointRemovedEvent extends DebugEvent {
+  Breakpoint get breakpoint;
+}
+abstract class InspectEvent extends DebugEvent {
+  InstanceRef get inspectee;
+}
+abstract class NoneEvent extends DebugEvent {}
+abstract class GCEvent extends IsolateEvent {}
+abstract class ExtensionEvent extends Event {
+  IsolateRef get isolate;
+  String get extensionKind;
+  ExtensionData get extensionData;
+}
+abstract class TimelineEventsEvent extends IsolateEvent {
+  Iterable<TimelineEvent> get timelineEvents;
+}
+abstract class ConnectionClosedEvent extends Event {
+  String get reason;
+}
diff --git a/runtime/observatory/lib/src/models/objects/extension_data.dart b/runtime/observatory/lib/src/models/objects/extension_data.dart
new file mode 100644
index 00000000000..5000a9b901f
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/extension_data.dart
@@ -0,0 +1,7 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class ExtensionData implements Map<String, dynamic> {}
diff --git a/runtime/observatory/lib/src/models/objects/frame.dart b/runtime/observatory/lib/src/models/objects/frame.dart
new file mode 100644
index 00000000000..d8e87cd362f
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/frame.dart
@@ -0,0 +1,7 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class Frame {}
diff --git a/runtime/observatory/lib/src/models/objects/instance.dart b/runtime/observatory/lib/src/models/objects/instance.dart
new file mode 100644
index 00000000000..b337f790fc2
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/instance.dart
@@ -0,0 +1,7 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class InstanceRef extends ObjectRef {}
diff --git a/runtime/observatory/lib/src/models/objects/library.dart b/runtime/observatory/lib/src/models/objects/library.dart
new file mode 100644
index 00000000000..6543ef9e8b7
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/library.dart
@@ -0,0 +1,33 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class LibraryRef extends ObjectRef {
+  /// The name of this library.
+  String get name;
+
+  /// The uri of this library.
+  String get uri;
+}
+
+abstract class Library extends Object implements LibraryRef {
+  /// Is this library debuggable? Default true.
+  bool get debuggable;
+
+  /// A list of the imports for this library.
+  //LibraryDependency[] dependencies;
+
+  // A list of the scripts which constitute this library.
+  Iterable<ScriptRef> get scripts;
+
+  // A list of the top-level variables in this library.
+  //List<FieldRef> get variables;
+
+  // A list of the top-level functions in this library.
+  //List<FunctionRef> get functions;
+
+  // A list of all classes in this library.
+  Iterable<ClassRef> get classes;
+}
diff --git a/runtime/observatory/lib/src/models/objects/notification.dart b/runtime/observatory/lib/src/models/objects/notification.dart
new file mode 100644
index 00000000000..9a9f8afbfd4
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/notification.dart
@@ -0,0 +1,17 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class Notification {}
+
+abstract class ExceptionNotification implements Notification{
+  Exception get exception;
+  /// [optional]
+  StackTrace get stacktrace;
+}
+
+abstract class EventNotification implements Notification{
+  Event get event;
+}
diff --git a/runtime/observatory/lib/src/models/objects/script.dart b/runtime/observatory/lib/src/models/objects/script.dart
new file mode 100644
index 00000000000..274fb08205e
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/script.dart
@@ -0,0 +1,22 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class ScriptRef extends ObjectRef {
+  /// The uri from which this script was loaded.
+  String get uri;
+}
+
+abstract class Script extends Object implements ScriptRef {
+  /// The library which owns this script.
+  // LibraryRef get library;
+
+  /// The source code for this script. For certain built-in scripts,
+  /// this may be reconstructed without source comments.
+  String get source;
+
+  int tokenToLine(int token);
+  int tokenToCol(int token);
+}
diff --git a/runtime/observatory/lib/src/models/objects/source_location.dart b/runtime/observatory/lib/src/models/objects/source_location.dart
new file mode 100644
index 00000000000..5d35d57be62
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/source_location.dart
@@ -0,0 +1,14 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class SourceLocation {
+  /// The script containing the source location.
+  ScriptRef get script;
+  /// The first token of the location.
+  int get tokenPos;
+  /// The last token of the location if this is a range. [optional]
+  int get endTokenPos;
+}
diff --git a/runtime/observatory/lib/src/models/objects/timeline_event.dart b/runtime/observatory/lib/src/models/objects/timeline_event.dart
new file mode 100644
index 00000000000..6cac6d10822
--- /dev/null
+++ b/runtime/observatory/lib/src/models/objects/timeline_event.dart
@@ -0,0 +1,7 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class TimelineEvent implements Map<String, dynamic> {}
diff --git a/runtime/observatory/lib/src/models/repositories/notification.dart b/runtime/observatory/lib/src/models/repositories/notification.dart
new file mode 100644
index 00000000000..9ab354362d3
--- /dev/null
+++ b/runtime/observatory/lib/src/models/repositories/notification.dart
@@ -0,0 +1,16 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of models;
+
+abstract class NotificationChangeEvent {
+  NotificationRepository get repository;
+}
+
+abstract class NotificationRepository {
+  Stream<NotificationChangeEvent> get onChange;
+  Iterable<Notification> list();
+  void delete(Notification);
+  void deleteAll();
+}
diff --git a/runtime/observatory/lib/src/repositories/notification.dart b/runtime/observatory/lib/src/repositories/notification.dart
new file mode 100644
index 00000000000..348dbca5513
--- /dev/null
+++ b/runtime/observatory/lib/src/repositories/notification.dart
@@ -0,0 +1,72 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file
+
+part of repositories;
+
+class NotificationChangeEvent implements M.NotificationChangeEvent {
+  final NotificationRepository repository;
+  NotificationChangeEvent(this.repository);
+}
+
+class NotificationRepository implements M.NotificationRepository {
+  final List<M.Notification> _list = new List<M.Notification>();
+
+  final StreamController<M.NotificationChangeEvent> _onChange =
+      new StreamController<M.NotificationChangeEvent>.broadcast();
+  Stream<M.NotificationChangeEvent> get onChange => _onChange.stream;
+
+  void add(M.Notification notification) {
+    assert(notification != null);
+    _list.add(notification);
+    _notify();
+  }
+
+  Iterable<M.Notification> list() => _list;
+
+  void delete(M.Notification notification) {
+    if (_list.remove(notification))
+    _notify();
+  }
+
+  void deleteAll() {
+    if (_list.isNotEmpty) {
+      _list.clear();
+      _notify();
+    }
+  }
+
+  NotificationRepository();
+
+  void _notify() {
+    _onChange.add(new NotificationChangeEvent(this));
+  }
+
+  void deleteWhere(bool test(M.Notification element)) {
+    int length = _list.length;
+    _list.removeWhere(test);
+    if (_list.length != length) _notify();
+  }
+
+  void deletePauseEvents({M.Isolate isolate}) {
+    if (isolate == null) {
+      deleteWhere((notification) {
+        return notification is M.EventNotification &&
+               M.Event.isPauseEvent(notification.event);
+      });
+    } else {
+      deleteWhere((notification) {
+        return notification is M.EventNotification &&
+               M.Event.isPauseEvent(notification.event) &&
+               notification.event.isolate == isolate;
+      });
+    }
+  }
+
+  void deleteDisconnectEvents() {
+    deleteWhere((notification) {
+      return notification is M.EventNotification &&
+             notification.event is M.ConnectionClosedEvent;
+    });
+  }
+}
diff --git a/runtime/observatory/lib/src/service/object.dart b/runtime/observatory/lib/src/service/object.dart
index 3491825352d..4110e923f26 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -22,14 +22,14 @@ Future cancelFutureSubscription(
 
 /// An RpcException represents an exceptional event that happened
 /// while invoking an rpc.
-abstract class RpcException implements Exception {
+abstract class RpcException implements Exception, M.BasicException {
   RpcException(this.message);
 
   String message;
 }
 
 /// A ServerRpcException represents an error returned by the VM.
-class ServerRpcException extends RpcException {
+class ServerRpcException extends RpcException implements M.RequestException {
   /// A list of well-known server error codes.
   static const kParseError     = -32700;
   static const kInvalidRequest = -32600;
@@ -70,7 +70,8 @@ class ServerRpcException extends RpcException {
 
 /// A NetworkRpcException is used to indicate that an rpc has
 /// been canceled due to network error.
-class NetworkRpcException extends RpcException {
+class NetworkRpcException extends RpcException
+                          implements M.ConnectionException {
   NetworkRpcException(String message) : super(message);
 
   String toString() => 'NetworkRpcException(${message})';
@@ -424,7 +425,8 @@ abstract class Location  {
 }
 
 /// A [SourceLocation] represents a location or range in the source code.
-class SourceLocation extends ServiceObject implements Location {
+class SourceLocation extends ServiceObject implements Location,
+                                                          M.SourceLocation {
   Script script;
   int tokenPos;
   int endTokenPos;
@@ -1119,7 +1121,7 @@ class HeapSnapshot {
 }
 
 /// State for a running isolate.
-class Isolate extends ServiceObjectOwner implements M.IsolateRef {
+class Isolate extends ServiceObjectOwner implements M.Isolate {
   static const kLoggingStream = '_Logging';
   static const kExtensionStream = 'Extension';
 
@@ -2036,7 +2038,7 @@ class ServiceEvent extends ServiceObject {
   }
 }
 
-class Breakpoint extends ServiceObject {
+class Breakpoint extends ServiceObject implements M.Breakpoint {
   Breakpoint._empty(ServiceObjectOwner owner) : super._empty(owner);
 
   // TODO(turnidge): Add state to track if a breakpoint has been
@@ -2132,7 +2134,7 @@ class LibraryDependency {
 }
 
 
-class Library extends HeapObject {
+class Library extends HeapObject implements M.LibraryRef {
   @observable String uri;
   @reflectable final dependencies = new ObservableList<LibraryDependency>();
   @reflectable final scripts = new ObservableList<Script>();
@@ -2929,7 +2931,7 @@ class LocalVarLocation {
   LocalVarLocation(this.line, this.column, this.endColumn);
 }
 
-class Script extends HeapObject {
+class Script extends HeapObject implements M.Script {
   final lines = new ObservableList<ScriptLine>();
   @observable String uri;
   @observable String kind;
@@ -2940,6 +2942,8 @@ class Script extends HeapObject {
   @observable int columnOffset;
   @observable Library library;
 
+  String source;
+
   bool get immutable => true;
 
   String _shortUri;
@@ -3041,6 +3045,7 @@ class Script extends HeapObject {
     lineOffset = map['lineOffset'];
     columnOffset = map['columnOffset'];
     _parseTokenPosTable(map['tokenPosTable']);
+    source = map['source'];
     _processSource(map['source']);
     library = map['library'];
   }
@@ -3998,7 +4003,7 @@ class MetricPoller {
   }
 }
 
-class Frame extends ServiceObject {
+class Frame extends ServiceObject implements M.Frame {
   @observable int index;
   @observable ServiceFunction function;
   @observable SourceLocation location;
diff --git a/runtime/observatory/observatory_sources.gypi b/runtime/observatory/observatory_sources.gypi
index ddade9118d2..d187645a8b4 100644
--- a/runtime/observatory/observatory_sources.gypi
+++ b/runtime/observatory/observatory_sources.gypi
@@ -16,6 +16,7 @@
     'lib/mocks.dart',
     'lib/models.dart',
     'lib/object_graph.dart',
+    'lib/repositories.dart',
     'lib/service.dart',
     'lib/service_common.dart',
     'lib/service_html.dart',
@@ -124,14 +125,18 @@
     'lib/src/elements/nav_bar.dart',
     'lib/src/elements/nav_bar.html',
     'lib/src/elements/nav/bar.dart',
-    'lib/src/elements/nav/isolate_menu.dart',
-    'lib/src/elements/nav/isolate_menu_wrapper.dart',
     'lib/src/elements/nav/class_menu.dart',
     'lib/src/elements/nav/class_menu_wrapper.dart',
-    'lib/src/elements/nav/menu.dart',
-    'lib/src/elements/nav/menu_wrapper.dart',
+    'lib/src/elements/nav/isolate_menu.dart',
+    'lib/src/elements/nav/isolate_menu_wrapper.dart',
     'lib/src/elements/nav/menu_item.dart',
     'lib/src/elements/nav/menu_item_wrapper.dart',
+    'lib/src/elements/nav/menu.dart',
+    'lib/src/elements/nav/menu_wrapper.dart',
+    'lib/src/elements/nav/notify_event.dart',
+    'lib/src/elements/nav/notify_exception.dart',
+    'lib/src/elements/nav/notify.dart',
+    'lib/src/elements/nav/notify_wrapper.dart',
     'lib/src/elements/nav/refresh.dart',
     'lib/src/elements/nav/refresh_wrapper.dart',
     'lib/src/elements/nav/top_menu.dart',
@@ -147,7 +152,6 @@
     'lib/src/elements/observatory_application.dart',
     'lib/src/elements/observatory_application.html',
     'lib/src/elements/observatory_element.dart',
-    'lib/src/elements/observatory_element.html',
     'lib/src/elements/persistent_handles.dart',
     'lib/src/elements/persistent_handles.html',
     'lib/src/elements/ports.dart',
@@ -168,23 +172,43 @@
     'lib/src/elements/timeline_page.dart',
     'lib/src/elements/timeline_page.html',
     'lib/src/elements/view_footer.dart',
+    'lib/src/elements/vm_connect_target.dart',
+    'lib/src/elements/vm_connect_target_wrapper.dart',
     'lib/src/elements/vm_connect.dart',
     'lib/src/elements/vm_connect.html',
     'lib/src/elements/vm_ref.dart',
     'lib/src/elements/vm_ref.html',
     'lib/src/elements/vm_view.dart',
     'lib/src/elements/vm_view.html',
+    'lib/src/mocks/exceptions/connection_exception.dart',
+    'lib/src/mocks/objects/error.dart',
     'lib/src/mocks/objects/event.dart',
     'lib/src/mocks/objects/class.dart',
     'lib/src/mocks/objects/isolate.dart',
-    'lib/src/mocks/objects/target.dart',
+    'lib/src/mocks/objects/notification.dart',
+    'lib/src/mocks/objects/script.dart',
+    'lib/src/mocks/objects/source_location.dart',
     'lib/src/mocks/objects/vm.dart',
-    'lib/src/models/objects/event.dart',
+    'lib/src/mocks/repositories/notification.dart',
+    'lib/src/models/exceptions.dart',
+    'lib/src/models/objects/breakpoint.dart',
     'lib/src/models/objects/class.dart',
+    'lib/src/models/objects/error.dart',
+    'lib/src/models/objects/event.dart',
+    'lib/src/models/objects/extension_data.dart',
+    'lib/src/models/objects/frame.dart',
+    'lib/src/models/objects/instance.dart',
     'lib/src/models/objects/isolate.dart',
+    'lib/src/models/objects/library.dart',
+    'lib/src/models/objects/notification.dart',
     'lib/src/models/objects/object.dart',
+    'lib/src/models/objects/script.dart',
+    'lib/src/models/objects/source_location.dart',
     'lib/src/models/objects/target.dart',
+    'lib/src/models/objects/timeline_event.dart',
     'lib/src/models/objects/vm.dart',
+    'lib/src/models/repositories/notification.dart',
+    'lib/src/repositories/notification.dart',
     'lib/src/service/object.dart',
     'lib/tracer.dart',
     'lib/utils.dart',
diff --git a/runtime/observatory/tests/observatory_ui/nav/notify/element_test.dart b/runtime/observatory/tests/observatory_ui/nav/notify/element_test.dart
new file mode 100644
index 00000000000..64adcfb8087
--- /dev/null
+++ b/runtime/observatory/tests/observatory_ui/nav/notify/element_test.dart
@@ -0,0 +1,121 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+import 'dart:html' hide Notification, NotificationEvent;
+import 'package:unittest/unittest.dart';
+import 'package:observatory/mocks.dart';
+import 'package:observatory/models.dart' as M;
+import 'package:observatory/src/elements/nav/notify.dart';
+import 'package:observatory/src/elements/nav/notify_event.dart';
+import 'package:observatory/src/elements/nav/notify_exception.dart';
+
+main() {
+  NavNotifyElement.tag.ensureRegistration();
+
+  final evTag = NavNotifyEventElement.tag.name;
+  final exTag = NavNotifyExceptionElement.tag.name;
+
+  const vm = const VMRefMock();
+  const isolate = const IsolateRefMock(id: 'i-id', name: 'i-name');
+
+  group('instantiation', () {
+    test('default', () {
+      final NavNotifyElement e = new NavNotifyElement(
+          new NotificationRepositoryMock());
+      expect(e, isNotNull, reason: 'element correctly created');
+      expect(e.notifyOnPause, isTrue, reason: 'notifyOnPause is default');
+    });
+    test('notify on pause', () {
+      final NavNotifyElement e = new NavNotifyElement(
+          new NotificationRepositoryMock(), notifyOnPause: true);
+      expect(e, isNotNull, reason: 'element correctly created');
+      expect(e.notifyOnPause, isTrue, reason: 'notifyOnPause is the same');
+    });
+    test('do not notify on pause', () {
+      final NavNotifyElement e = new NavNotifyElement(
+          new NotificationRepositoryMock(), notifyOnPause: false);
+      expect(e, isNotNull, reason: 'element correctly created');
+      expect(e.notifyOnPause, isFalse, reason: 'notifyOnPause is the same');
+    });
+  });
+  test('is correctly listening', () async {
+    final NotificationRepositoryMock repository =
+        new NotificationRepositoryMock();
+    final NavNotifyElement e = new NavNotifyElement(repository);
+    document.body.append(e);
+    await e.onRendered.first;
+    expect(repository.hasListeners, isTrue, reason: 'is listening');
+    e.remove();
+    await e.onRendered.first;
+    expect(repository.hasListeners, isFalse, reason: 'is no more listening');
+  });
+  group('elements', () {
+    test('created after attachment', () async {
+      final NotificationRepositoryMock repository =
+          new NotificationRepositoryMock(list: [
+            new ExceptionNotificationMock(exception: new Exception("ex")),
+            const EventNotificationMock(event: const VMUpdateEventMock(vm: vm)),
+            const EventNotificationMock(event: const VMUpdateEventMock(vm: vm))
+          ]);
+      final NavNotifyElement e = new NavNotifyElement(repository);
+      document.body.append(e);
+      await e.onRendered.first;
+      expect(repository.listInvoked, isTrue, reason: 'should invoke list()');
+      expect(e.children.length, isNonZero, reason: 'has elements');
+      expect(e.querySelectorAll(evTag).length, equals(2));
+      expect(e.querySelectorAll(exTag).length, equals(1));
+      e.remove();
+      await e.onRendered.first;
+      expect(e.children.length, isZero, reason: 'is empty');
+    });
+    test('react to notifyOnPause change', () async {
+      final NotificationRepositoryMock repository =
+          new NotificationRepositoryMock(list: [
+            new ExceptionNotificationMock(exception: new Exception("ex")),
+            const EventNotificationMock(event: const VMUpdateEventMock()),
+            const EventNotificationMock(
+                event: const PauseStartEventMock(isolate: isolate))
+          ]);
+      final NavNotifyElement e = new NavNotifyElement(repository,
+          notifyOnPause: true);
+      document.body.append(e);
+      await e.onRendered.first;
+      expect(e.querySelectorAll(evTag).length, equals(2));
+      expect(e.querySelectorAll(exTag).length, equals(1));
+      e.notifyOnPause = false;
+      await e.onRendered.first;
+      expect(e.querySelectorAll(evTag).length, equals(1));
+      expect(e.querySelectorAll(exTag).length, equals(1));
+      e.notifyOnPause = true;
+      await e.onRendered.first;
+      expect(e.querySelectorAll(evTag).length, equals(2));
+      expect(e.querySelectorAll(exTag).length, equals(1));
+      e.remove();
+      await e.onRendered.first;
+      expect(e.children.length, isZero, reason: 'is empty');
+    });
+    test('react to update event', () async {
+      final List<M.Notification> list = [
+        new ExceptionNotificationMock(exception: new Exception("ex")),
+        const EventNotificationMock(event: const VMUpdateEventMock()),
+      ];
+      final NotificationRepositoryMock repository =
+          new NotificationRepositoryMock(list: list);
+      final NavNotifyElement e = new NavNotifyElement(repository,
+          notifyOnPause: true);
+      document.body.append(e);
+      await e.onRendered.first;
+      expect(e.querySelectorAll(evTag).length, equals(1));
+      expect(e.querySelectorAll(exTag).length, equals(1));
+      list.add(const EventNotificationMock(
+          event: const PauseStartEventMock(isolate: isolate)));
+      repository.triggerChangeEvent();
+      await e.onRendered.first;
+      expect(e.querySelectorAll(evTag).length, equals(2));
+      expect(e.querySelectorAll(exTag).length, equals(1));
+      e.remove();
+      await e.onRendered.first;
+      expect(e.children.length, isZero, reason: 'is empty');
+    });
+  });
+}
diff --git a/runtime/observatory/tests/observatory_ui/nav/notify/element_test.html b/runtime/observatory/tests/observatory_ui/nav/notify/element_test.html
new file mode 100644
index 00000000000..f0e956daa16
--- /dev/null
+++ b/runtime/observatory/tests/observatory_ui/nav/notify/element_test.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta http-equiv="X-UA-Compatible" content="IE=edge">
+  <meta name="dart.unittest" content="full-stack-traces">
+  <style>
+     .unittest-table { font-family:monospace; border:1px; }
+     .unittest-pass { background: #6b3;}
+     .unittest-fail { background: #d55;}
+     .unittest-error { background: #a11;}
+  </style>
+  <script src="/packages/web_components/webcomponents.js"></script>
+  <script src="/packages/web_components/dart_support.js"></script>
+</head>
+<body>
+  <script type="text/javascript"
+      src="/root_dart/tools/testing/dart/test_controller.js"></script>
+  %TEST_SCRIPTS%
+</body>
+</html>
diff --git a/runtime/observatory/tests/observatory_ui/nav/notify_event/element_test.dart b/runtime/observatory/tests/observatory_ui/nav/notify_event/element_test.dart
new file mode 100644
index 00000000000..5d5de5c89f8
--- /dev/null
+++ b/runtime/observatory/tests/observatory_ui/nav/notify_event/element_test.dart
@@ -0,0 +1,65 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+import 'dart:html';
+import 'dart:async';
+import 'package:unittest/unittest.dart';
+import 'package:observatory/mocks.dart';
+import 'package:observatory/src/elements/nav/notify_event.dart';
+
+main() {
+  NavNotifyEventElement.tag.ensureRegistration();
+
+  final PauseStartEventMock event = new PauseStartEventMock(
+              isolate: new IsolateMock(id: 'isolate-id', name: 'isolate-name'));
+  group('instantiation', () {
+    final NavNotifyEventElement e = new NavNotifyEventElement(event);
+    expect(e, isNotNull, reason: 'element correctly created');
+    expect(e.event, equals(event));
+  });
+  group('elements', () {
+    test('created after attachment', () async {
+      final NavNotifyEventElement e = new NavNotifyEventElement(event);
+      document.body.append(e);
+      await e.onRendered.first;
+      expect(e.children.length, isNonZero, reason: 'has elements');
+      e.remove();
+      await e.onRendered.first;
+      expect(e.children.length, isZero, reason: 'is empty');
+    });
+  });
+  group('events are fired', () {
+    NavNotifyEventElement e;
+    StreamSubscription sub;
+    setUp(() async {
+      e = new NavNotifyEventElement(event);
+      document.body.append(e);
+      await e.onRendered.first;
+    });
+    tearDown(() {
+      sub.cancel();
+      e.remove();
+    });
+    test('navigation after connect', () async {
+      sub = window.onPopState.listen(expectAsync((_) {}, count: 1,
+        reason: 'event is fired'));
+      e.querySelector('a').click();
+    });
+    test('onDelete events (DOM)', () async {
+      sub = e.onDelete.listen(expectAsync((EventDeleteEvent ev) {
+        expect(ev, isNotNull, reason: 'event is passed');
+        expect(ev.event, equals(event),
+                                            reason: 'exception is the same');
+      }, count: 1, reason: 'event is fired'));
+      e.querySelector('button').click();
+    });
+    test('onDelete events (code)', () async {
+      sub = e.onDelete.listen(expectAsync((EventDeleteEvent ev) {
+        expect(ev, isNotNull, reason: 'event is passed');
+        expect(ev.event, equals(event),
+                                            reason: 'exception is the same');
+      }, count: 1, reason: 'event is fired'));
+      e.delete();
+    });
+  });
+}
diff --git a/runtime/observatory/tests/observatory_ui/nav/notify_event/element_test.html b/runtime/observatory/tests/observatory_ui/nav/notify_event/element_test.html
new file mode 100644
index 00000000000..f0e956daa16
--- /dev/null
+++ b/runtime/observatory/tests/observatory_ui/nav/notify_event/element_test.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta http-equiv="X-UA-Compatible" content="IE=edge">
+  <meta name="dart.unittest" content="full-stack-traces">
+  <style>
+     .unittest-table { font-family:monospace; border:1px; }
+     .unittest-pass { background: #6b3;}
+     .unittest-fail { background: #d55;}
+     .unittest-error { background: #a11;}
+  </style>
+  <script src="/packages/web_components/webcomponents.js"></script>
+  <script src="/packages/web_components/dart_support.js"></script>
+</head>
+<body>
+  <script type="text/javascript"
+      src="/root_dart/tools/testing/dart/test_controller.js"></script>
+  %TEST_SCRIPTS%
+</body>
+</html>
diff --git a/runtime/observatory/tests/observatory_ui/nav/notify_exception/connection_exception_test.dart b/runtime/observatory/tests/observatory_ui/nav/notify_exception/connection_exception_test.dart
new file mode 100644
index 00000000000..e6b3bc2552d
--- /dev/null
+++ b/runtime/observatory/tests/observatory_ui/nav/notify_exception/connection_exception_test.dart
@@ -0,0 +1,67 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+import 'dart:html';
+import 'dart:async';
+import 'package:unittest/unittest.dart';
+import 'package:observatory/models.dart';
+import 'package:observatory/mocks.dart';
+import 'package:observatory/src/elements/nav/notify_exception.dart';
+
+main() {
+  NavNotifyExceptionElement.tag.ensureRegistration();
+
+  final ConnectionException exception =
+      new ConnectionExceptionMock(message: 'message');
+  test('instantiation', () {
+    final NavNotifyExceptionElement e =
+                                new NavNotifyExceptionElement(exception);
+    expect(e, isNotNull, reason: 'element correctly created');
+  });
+  test('elements created after attachment', () async {
+    final NavNotifyExceptionElement e =
+                                new NavNotifyExceptionElement(exception);
+    document.body.append(e);
+    await e.onRendered.first;
+    expect(e.children.length, isNonZero, reason: 'has elements');
+    e.remove();
+    await e.onRendered.first;
+    expect(e.children.length, isZero, reason: 'is empty');
+  });
+  group('events are fired', () {
+    NavNotifyExceptionElement e;
+    StreamSubscription sub;
+    setUp(() async {
+      e = new NavNotifyExceptionElement(exception);
+      document.body.append(e);
+      await e.onRendered.first;
+    });
+    tearDown(() {
+      sub.cancel();
+      e.remove();
+    });
+    test('navigation after connect', () async {
+      sub = window.onPopState.listen(expectAsync((_) {}, count: 1,
+        reason: 'event is fired'));
+      e.querySelector('a').click();
+    });
+    test('onDelete events (DOM)', () async {
+      sub = e.onDelete.listen(expectAsync((ExceptionDeleteEvent event) {
+        expect(event, isNotNull, reason: 'event is passed');
+        expect(event.exception, equals(exception),
+                                              reason: 'exception is the same');
+        expect(event.stacktrace, isNull);
+      }, count: 1, reason: 'event is fired'));
+      e.querySelector('button').click();
+    });
+    test('onDelete events (code)', () async {
+      sub = e.onDelete.listen(expectAsync((ExceptionDeleteEvent event) {
+        expect(event, isNotNull, reason: 'event is passed');
+        expect(event.exception, equals(exception),
+                                              reason: 'exception is the same');
+        expect(event.stacktrace, isNull);
+      }, count: 1, reason: 'event is fired'));
+      e.delete();
+    });
+  });
+}
diff --git a/runtime/observatory/tests/observatory_ui/nav/notify_exception/connection_exception_test.html b/runtime/observatory/tests/observatory_ui/nav/notify_exception/connection_exception_test.html
new file mode 100644
index 00000000000..f0e956daa16
--- /dev/null
+++ b/runtime/observatory/tests/observatory_ui/nav/notify_exception/connection_exception_test.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta http-equiv="X-UA-Compatible" content="IE=edge">
+  <meta name="dart.unittest" content="full-stack-traces">
+  <style>
+     .unittest-table { font-family:monospace; border:1px; }
+     .unittest-pass { background: #6b3;}
+     .unittest-fail { background: #d55;}
+     .unittest-error { background: #a11;}
+  </style>
+  <script src="/packages/web_components/webcomponents.js"></script>
+  <script src="/packages/web_components/dart_support.js"></script>
+</head>
+<body>
+  <script type="text/javascript"
+      src="/root_dart/tools/testing/dart/test_controller.js"></script>
+  %TEST_SCRIPTS%
+</body>
+</html>
diff --git a/runtime/observatory/tests/observatory_ui/nav/notify_exception/exception_test.dart b/runtime/observatory/tests/observatory_ui/nav/notify_exception/exception_test.dart
new file mode 100644
index 00000000000..be9fdc5fdac
--- /dev/null
+++ b/runtime/observatory/tests/observatory_ui/nav/notify_exception/exception_test.dart
@@ -0,0 +1,96 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+import 'dart:html';
+import 'dart:async';
+import 'package:unittest/unittest.dart';
+import 'package:observatory/src/elements/nav/notify_exception.dart';
+
+main() {
+  NavNotifyExceptionElement.tag.ensureRegistration();
+
+  final StackTrace stacktrace = new StackTrace.fromString('stacktrace string');
+  group('normal exception', () {
+    final Exception exception = new Exception('exception message');
+    group('instantiation', () {
+      test('no stacktrace', () {
+        final NavNotifyExceptionElement e =
+                                      new NavNotifyExceptionElement(exception);
+        expect(e, isNotNull, reason: 'element correctly created');
+        expect(e.exception, equals(exception));
+        expect(e.stacktrace, isNull);
+      });
+      test('with stacktrace', () {
+        final NavNotifyExceptionElement e =
+              new NavNotifyExceptionElement(exception, stacktrace: stacktrace);
+        expect(e, isNotNull, reason: 'element correctly created');
+        expect(e.exception, equals(exception));
+        expect(e.stacktrace, equals(stacktrace));
+      });
+    });
+    group('elements', () {
+      test('created after attachment (no stacktrace)', () async {
+        final NavNotifyExceptionElement e =
+                                      new NavNotifyExceptionElement(exception);
+        document.body.append(e);
+        await e.onRendered.first;
+        expect(e.children.length, isNonZero, reason: 'has elements');
+        expect(e.innerHtml.contains(exception.toString()), isTrue);
+        expect(e.innerHtml.contains(stacktrace.toString()), isFalse);
+        e.remove();
+        await e.onRendered.first;
+        expect(e.children.length, isZero, reason: 'is empty');
+      });
+      test('created after attachment (with stacktrace)', () async {
+        final NavNotifyExceptionElement e =
+              new NavNotifyExceptionElement(exception, stacktrace: stacktrace);
+        document.body.append(e);
+        await e.onRendered.first;
+        expect(e.children.length, isNonZero, reason: 'has elements');
+        expect(e.innerHtml.contains(exception.toString()), isTrue);
+        expect(e.innerHtml.contains(stacktrace.toString()), isTrue);
+        e.remove();
+        await e.onRendered.first;
+        expect(e.children.length, isZero, reason: 'is empty');
+      });
+    });
+    group('events are fired', () {
+      NavNotifyExceptionElement e;
+      StreamSubscription sub;
+      setUp(() async {
+        e = new NavNotifyExceptionElement(exception, stacktrace: stacktrace);
+        document.body.append(e);
+        await e.onRendered.first;
+      });
+      tearDown(() {
+        sub.cancel();
+        e.remove();
+      });
+      test('navigation after connect', () async {
+        sub = window.onPopState.listen(expectAsync((_) {}, count: 1,
+          reason: 'event is fired'));
+        e.querySelector('a').click();
+      });
+      test('onDelete events (DOM)', () async {
+        sub = e.onDelete.listen(expectAsync((ExceptionDeleteEvent event) {
+          expect(event, isNotNull, reason: 'event is passed');
+          expect(event.exception, equals(exception),
+                                              reason: 'exception is the same');
+          expect(event.stacktrace, equals(stacktrace),
+                                            reason: 'stacktrace is the same');
+        }, count: 1, reason: 'event is fired'));
+        e.querySelector('button').click();
+      });
+      test('onDelete events (code)', () async {
+        sub = e.onDelete.listen(expectAsync((ExceptionDeleteEvent event) {
+          expect(event, isNotNull, reason: 'event is passed');
+          expect(event.exception, equals(exception),
+                                              reason: 'exception is the same');
+          expect(event.stacktrace, equals(stacktrace),
+                                            reason: 'stacktrace is the same');
+        }, count: 1, reason: 'event is fired'));
+        e.delete();
+      });
+    });
+  });
+}
diff --git a/runtime/observatory/tests/observatory_ui/nav/notify_exception/exception_test.html b/runtime/observatory/tests/observatory_ui/nav/notify_exception/exception_test.html
new file mode 100644
index 00000000000..f0e956daa16
--- /dev/null
+++ b/runtime/observatory/tests/observatory_ui/nav/notify_exception/exception_test.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta http-equiv="X-UA-Compatible" content="IE=edge">
+  <meta name="dart.unittest" content="full-stack-traces">
+  <style>
+     .unittest-table { font-family:monospace; border:1px; }
+     .unittest-pass { background: #6b3;}
+     .unittest-fail { background: #d55;}
+     .unittest-error { background: #a11;}
+  </style>
+  <script src="/packages/web_components/webcomponents.js"></script>
+  <script src="/packages/web_components/dart_support.js"></script>
+</head>
+<body>
+  <script type="text/javascript"
+      src="/root_dart/tools/testing/dart/test_controller.js"></script>
+  %TEST_SCRIPTS%
+</body>
+</html>