diff --git a/dom/media/MediaStreamGraph.cpp b/dom/media/MediaStreamGraph.cpp
index 2816d94f3e63..b406e94a38c7 100644
--- a/dom/media/MediaStreamGraph.cpp
+++ b/dom/media/MediaStreamGraph.cpp
@@ -1000,7 +1000,21 @@ MediaStreamGraphImpl::AllFinishedStreamsNotified()
 }
 
 void
-MediaStreamGraphImpl::UpdateGraph(GraphTime aEndBlockingDecisions)
+MediaStreamGraphImpl::RunMessageAfterProcessing(nsAutoPtr<ControlMessage> aMessage)
+{
+  MOZ_ASSERT(CurrentDriver()->OnThread());
+
+  if (mFrontMessageQueue.IsEmpty()) {
+    mFrontMessageQueue.AppendElement();
+  }
+
+  // Only one block is used for messages from the graph thread.
+  MOZ_ASSERT(mFrontMessageQueue.Length() == 1);
+  mFrontMessageQueue[0].mMessages.AppendElement(Move(aMessage));
+}
+
+void
+MediaStreamGraphImpl::RunMessagesInQueue()
 {
   // Calculate independent action times for each batch of messages (each
   // batch corresponding to an event loop task). This isolates the performance
@@ -1013,7 +1027,11 @@ MediaStreamGraphImpl::UpdateGraph(GraphTime aEndBlockingDecisions)
     }
   }
   mFrontMessageQueue.Clear();
+}
 
+void
+MediaStreamGraphImpl::UpdateGraph(GraphTime aEndBlockingDecisions)
+{
   MOZ_ASSERT(aEndBlockingDecisions >= mProcessedTime);
   // The next state computed time can be the same as the previous: it
   // means the driver would be have been blocking indefinitly, but the graph has
@@ -1204,6 +1222,9 @@ MediaStreamGraphImpl::OneIteration(GraphTime aStateEnd)
 {
   MaybeProduceMemoryReport();
 
+  // Process graph message from the main thread for this iteration.
+  RunMessagesInQueue();
+
   GraphTime stateEnd = std::min(aStateEnd, mEndTime);
   UpdateGraph(stateEnd);
 
@@ -1216,6 +1237,10 @@ MediaStreamGraphImpl::OneIteration(GraphTime aStateEnd)
 
   UpdateCurrentTimeForStreams(oldProcessedTime);
 
+  // Process graph messages queued from RunMessageAfterProcessing() on this
+  // thread during the iteration.
+  RunMessagesInQueue();
+
   return UpdateMainThreadState();
 }
 
diff --git a/dom/media/MediaStreamGraphImpl.h b/dom/media/MediaStreamGraphImpl.h
index a27857c54b86..c5e850ca6b3c 100644
--- a/dom/media/MediaStreamGraphImpl.h
+++ b/dom/media/MediaStreamGraphImpl.h
@@ -38,8 +38,11 @@ struct StreamUpdate
 };
 
 /**
- * This represents a message passed from the main thread to the graph thread.
- * A ControlMessage always has a weak reference a particular affected stream.
+ * This represents a message run on the graph thread to modify stream or graph
+ * state.  These are passed from main thread to graph thread through
+ * AppendMessage(), or scheduled on the graph thread with
+ * RunMessageAfterProcessing().  A ControlMessage
+ * always has a weak reference to a particular affected stream.
  */
 class ControlMessage
 {
@@ -58,6 +61,8 @@ public:
   // All stream data for times < mProcessedTime has already been
   // computed.
   virtual void Run() = 0;
+  // RunDuringShutdown() is only relevant to messages generated on the main
+  // thread (for AppendMessage()).
   // 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.
@@ -218,8 +223,12 @@ public:
    */
   void UpdateCurrentTimeForStreams(GraphTime aPrevCurrentTime);
   /**
-   * Process graph message for this iteration, update stream processing order,
-   * and recompute stream blocking until aEndBlockingDecisions.
+   * Process graph messages in mFrontMessageQueue.
+   */
+  void RunMessagesInQueue();
+  /**
+   * Update stream processing order and recompute stream blocking until
+   * aEndBlockingDecisions.
    */
   void UpdateGraph(GraphTime aEndBlockingDecisions);
 
@@ -242,6 +251,14 @@ public:
                            GraphTime aDesiredUpToTime,
                            bool* aEnsureNextIteration);
 
+  /**
+   * For use during ProcessedMediaStream::ProcessInput() or
+   * MediaStreamListener callbacks, when graph state cannot be changed.
+   * Schedules |aMessage| to run after processing, at a time when graph state
+   * can be changed.  Graph thread.
+   */
+  void RunMessageAfterProcessing(nsAutoPtr<ControlMessage> aMessage);
+
   /**
    * Called when a suspend/resume/close operation has been completed, on the
    * graph thread.