diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 674088352bf..8f4d3632dd3 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -27408,7 +27408,7 @@ class Window extends EventTarget implements WindowEventHandlers, WindowBase, Glo
    * [animationFrame] again for the animation to continue.
    */
   Future<num> get animationFrame {
-    var completer = new Completer<num>();
+    var completer = new Completer<num>.sync();
     requestAnimationFrame((time) {
       completer.complete(time);
     });
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 765bce0d707..8742ae2fc7d 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -28972,13 +28972,13 @@ class Url extends NativeFieldWrapperClass2 implements UrlUtils {
     if ((blob_OR_source_OR_stream is Blob || blob_OR_source_OR_stream == null)) {
       return _createObjectURL_1(blob_OR_source_OR_stream);
     }
-    if ((blob_OR_source_OR_stream is MediaSource || blob_OR_source_OR_stream == null)) {
+    if ((blob_OR_source_OR_stream is MediaStream || blob_OR_source_OR_stream == null)) {
       return _createObjectURL_2(blob_OR_source_OR_stream);
     }
-    if ((blob_OR_source_OR_stream is _WebKitMediaSource || blob_OR_source_OR_stream == null)) {
+    if ((blob_OR_source_OR_stream is MediaSource || blob_OR_source_OR_stream == null)) {
       return _createObjectURL_3(blob_OR_source_OR_stream);
     }
-    if ((blob_OR_source_OR_stream is MediaStream || blob_OR_source_OR_stream == null)) {
+    if ((blob_OR_source_OR_stream is _WebKitMediaSource || blob_OR_source_OR_stream == null)) {
       return _createObjectURL_4(blob_OR_source_OR_stream);
     }
     throw new ArgumentError("Incorrect number or type of arguments");
@@ -30049,7 +30049,7 @@ class Window extends EventTarget implements WindowEventHandlers, WindowBase, Glo
    * [animationFrame] again for the animation to continue.
    */
   Future<num> get animationFrame {
-    var completer = new Completer<num>();
+    var completer = new Completer<num>.sync();
     requestAnimationFrame((time) {
       completer.complete(time);
     });
diff --git a/tools/dom/templates/html/impl/impl_Window.darttemplate b/tools/dom/templates/html/impl/impl_Window.darttemplate
index d7dadf4408c..b84bb5f3fa4 100644
--- a/tools/dom/templates/html/impl/impl_Window.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Window.darttemplate
@@ -27,7 +27,7 @@ $endif
    * [animationFrame] again for the animation to continue.
    */
   Future<num> get animationFrame {
-    var completer = new Completer<num>();
+    var completer = new Completer<num>.sync();
     requestAnimationFrame((time) {
       completer.complete(time);
     });