Bug 1299172 - Fix media element StreamSizeListener calling DispatchToMainThreadAfterStreamStateUpdate off-MSG-thread. r=jesup

MozReview-Commit-ID: Cc2tJbEog20

--HG--
extra : rebase_source : 83731e3fe29a7813a51f70eff8a0f43a21f92e1d

dom/html/HTMLMediaElement.cpp

@@ -310,10 +310,13 @@ public:
       if (c->mFrame.GetIntrinsicSize() != gfx::IntSize(0,0)) {
         mInitialSizeFound = true;
         nsCOMPtr<nsIRunnable> event =
-          NewRunnableMethod<gfx::IntSize>(
-              this, &StreamSizeListener::ReceivedSize,
-              c->mFrame.GetIntrinsicSize());
-        aGraph->DispatchToMainThreadAfterStreamStateUpdate(event.forget());
+          NewRunnableMethod<gfx::IntSize>(this, &StreamSizeListener::ReceivedSize,
+                                          c->mFrame.GetIntrinsicSize());
+        // This is fine to dispatch straight to main thread (instead of via
+        // ...AfterStreamUpdate()) since it reflects state of the element,
+        // not the stream. Events reflecting stream or track state should be
+        // dispatched so their order is preserved.
+        NS_DispatchToMainThread(event.forget());
         return;
       }
     }