Display isolate message queue in Observatory debugger

- Log the parameters to RPCs
- Display messages like stack frames
    - handler function and script visible
    - message preview instead of local variables
- Expanded and previewed messages do not collapse when stepping within the existing message
- Mark patch classes as finalized to avoid ASSERT on class_finalizer.cc:2358 **
- Support iterating over message queues
- Support printing the message queue as JSON
- Inhibit OOB messages from being handled if we are iterating over the message queue
    - avoids dead lock when looking up port handler (done in Dart code with message handler locked) and a stack overflow trigger to handle OOB messages
- make getObject understand message ids
- Fix dartbug.com/23355

** Need to discuss with Ivan and Matthias (reviewed code differs from committed code but matches my fix):
https://codereview.chromium.org//828353002
https://code.google.com/p/dart/source/detail?r=42612

R=turnidge@google.com

Review URL: https://codereview.chromium.org//1122503003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@45505 260f80e4-7a28-3924-810f-c04153c831b5

runtime/vm/message_handler_test.cc

@@ -158,11 +158,25 @@ UNIT_TEST_CASE(MessageHandler_HasOOBMessages) {
   Message* message = new Message(1, NULL, 0, Message::kNormalPriority);
   handler_peer.PostMessage(message);
   EXPECT(!handler.HasOOBMessages());
+  {
+    // Acquire ownership of message handler queues, verify one regular message.
+    MessageHandler::AcquiredQueues aq;
+    handler.AcquireQueues(&aq);
+    EXPECT(aq.queue()->Length() == 1);
+  }
 
   // Post an oob message.
   message = new Message(1, NULL, 0, Message::kOOBPriority);
   handler_peer.PostMessage(message);
   EXPECT(handler.HasOOBMessages());
+  {
+    // Acquire ownership of message handler queues, verify one regular and one
+    // OOB message.
+    MessageHandler::AcquiredQueues aq;
+    handler.AcquireQueues(&aq);
+    EXPECT(aq.queue()->Length() == 1);
+    EXPECT(aq.oob_queue()->Length() == 1);
+  }
 
   // Delete all pending messages.
   handler_peer.CloseAllPorts();