DevTools: Async call stacks for window.postMessage()

Source/core/frame/LocalDOMWindow.cpp

Index: Source/core/frame/LocalDOMWindow.cpp
diff --git a/Source/core/frame/LocalDOMWindow.cpp b/Source/core/frame/LocalDOMWindow.cpp
index 2dc3725be32e1c28dbff75f461fc8f729da915e5..bed966c268feea02ca93fcada945df39cb68eb32 100644
--- a/Source/core/frame/LocalDOMWindow.cpp
+++ b/Source/core/frame/LocalDOMWindow.cpp
@@ -128,6 +128,7 @@ public:
         , m_stackTrace(stackTrace)
         , m_userGestureToken(userGestureToken)
     {
+        m_asyncOperationId = InspectorInstrumentation::traceAsyncOperationStarting(executionContext(), "postMessage");

[yurys, 2014/07/21 12:45:32]

If we are OK with storing async id in the instrumented instance, are you
planning to switch other async stacks instrumentation to the new API?

[aandrey, 2014/07/22 11:08:43]

Yes, something like ExecutionContextTask/FileSystemAPI should be easily
switchable, but for others like setTimeout/requestAnimFrame, we  would still
need to have a place to match timeoutId to asyncOperationId, so it makes no
sense to switch.

     }
 
     PassRefPtrWillBeRawPtr<MessageEvent> event()
@@ -142,8 +143,10 @@ public:
 private:
     virtual void fired() OVERRIDE
     {
+        InspectorInstrumentationCookie cookie = InspectorInstrumentation::traceAsyncOperationCompletedCallbackStarting(executionContext(), m_asyncOperationId);

[yurys, 2014/07/21 12:45:32]

Why do you need to merge two hooks into one?

[aandrey, 2014/07/22 11:08:43]

To have only one instrumentation call here. Actually this "combined" method is
the most useful, but should we want to expose it in public API we should
separate it to be flexible.

[yurys, 2014/07/22 13:09:43]

Why is it marked as completed only here? Shouldn't it be done where the
PostMessageTimer is created and scheduled?

[aandrey, 2014/07/22 13:32:14]

No, it's on the right place.
The async operation "completed" means that there will be no more callbacks, and
we can delete the async stack trace associated with the operation. Until this
place we do need that async stack and cannot say the operation is "completed"
before this place.

The traceAsyncOperationCompletedCallbackStarting actually does:
1) traceAsyncCallbackStarting    => we save the async stack as "current"
2) traceAsyncOperationCompleted  => we delete the async stack

         m_window->postMessageTimerFired(adoptPtr(this));
         // This object is deleted now.
+        InspectorInstrumentation::traceAsyncCallbackCompleted(cookie);
     }
 
     RefPtrWillBePersistent<LocalDOMWindow> m_window;
@@ -154,6 +157,7 @@ private:
     RefPtr<SecurityOrigin> m_targetOrigin;
     RefPtrWillBePersistent<ScriptCallStack> m_stackTrace;
     RefPtr<UserGestureToken> m_userGestureToken;
+    int m_asyncOperationId;
 };
 
 static void disableSuddenTermination()