b=1020411 correct control message order with RunAfterPendingUpdates() at shutdown r=roc

--HG--
extra : transplant_source : %AE%05%92%2C%60%9FL%D0%13O%EE%7D%09ZV%87%06%E9%B6%D8

content/media/MediaStreamGraph.cpp

@@ -1703,6 +1703,11 @@ MediaStreamGraphImpl::RunInStableState()
   for (uint32_t i = 0; i < controlMessagesToRunDuringShutdown.Length(); ++i) {
     controlMessagesToRunDuringShutdown[i]->RunDuringShutdown();
   }
+
+#ifdef DEBUG
+  mCanRunMessagesSynchronously = mDetectedNotRunning &&
+    mLifecycleState >= LIFECYCLE_WAITING_FOR_THREAD_SHUTDOWN;
+#endif
 }
 
 static NS_DEFINE_CID(kAppShellCID, NS_APPSHELL_CID);
@@ -1752,7 +1757,14 @@ MediaStreamGraphImpl::AppendMessage(ControlMessage* aMessage)
     // this message.
     // This should only happen during forced shutdown, or after a non-realtime
     // graph has finished processing.
+#ifdef DEBUG
+    MOZ_ASSERT(mCanRunMessagesSynchronously);
+    mCanRunMessagesSynchronously = false;
+#endif
     aMessage->RunDuringShutdown();
+#ifdef DEBUG
+    mCanRunMessagesSynchronously = true;
+#endif
     delete aMessage;
     if (IsEmpty() &&
         mLifecycleState >= LIFECYCLE_WAITING_FOR_STREAM_DESTRUCTION) {
@@ -2176,7 +2188,10 @@ MediaStream::RunAfterPendingUpdates(nsRefPtr<nsIRunnable> aRunnable)
     }
     virtual void RunDuringShutdown() MOZ_OVERRIDE
     {
-      mRunnable->Run();
+      // Don't run mRunnable now as it may call AppendMessage() which would
+      // assume that there are no remaining controlMessagesToRunDuringShutdown.
+      MOZ_ASSERT(NS_IsMainThread());
+      NS_DispatchToCurrentThread(mRunnable);
     }
   private:
     nsRefPtr<nsIRunnable> mRunnable;
@@ -2656,6 +2671,9 @@ MediaStreamGraphImpl::MediaStreamGraphImpl(bool aRealtime, TrackRate aSampleRate
   , mSelfRef(MOZ_THIS_IN_INITIALIZER_LIST())
   , mAudioStreamSizes()
   , mNeedsMemoryReport(false)
+#ifdef DEBUG
+  , mCanRunMessagesSynchronously(false)
+#endif
 {
 #ifdef PR_LOGGING
   if (!gMediaStreamGraphLog) {

content/media/MediaStreamGraph.h

@@ -382,7 +382,8 @@ public:
    * updates that were sent from the graph thread or will be sent before the
    * graph thread receives the next graph update.
    *
-   * If the graph has been shutdown or destroyed, or if it is non-realtime
+   * If the graph has been shut down or destroyed, then the runnable will be
+   * dispatched to the event queue immediately.  If the graph is non-realtime
    * and has not started, then the runnable will be run
    * synchronously/immediately.  (There are no pending updates in these
    * situations.)

content/media/MediaStreamGraphImpl.h

@@ -89,6 +89,7 @@ public:
   virtual void Run() = 0;
   // When we're shutting down the application, most messages are ignored but
   // some cleanup messages should still be processed (on the main thread).
+  // This must not add new control messages to the graph.
   virtual void RunDuringShutdown() {}
   MediaStream* GetStream() { return mStream; }
 
@@ -642,6 +643,14 @@ private:
    * Indicates that the MSG thread should gather data for a memory report.
    */
   bool mNeedsMemoryReport;
+
+#ifdef DEBUG
+  /**
+   * Used to assert when AppendMessage() runs ControlMessages synchronously.
+   */
+  bool mCanRunMessagesSynchronously;
+#endif
+
 };
 
 }