Bug 1161946 - MainThreadMediaStreamListener should be notified just when the stream is finished - patch 2, r=padenot

dom/media/MediaStreamGraph.cpp

@@ -1548,9 +1548,7 @@ MediaStreamGraphImpl::ApplyStreamUpdate(StreamUpdate* aUpdate)
       stream->mWrapper->NotifyStreamFinished();
     }
 
-    for (int32_t i = stream->mMainThreadListeners.Length() - 1; i >= 0; --i) {
-      stream->mMainThreadListeners[i]->NotifyMainThreadStreamFinished();
-    }
+    stream->NotifyMainThreadListeners();
   }
 }
 
@@ -2408,6 +2406,50 @@ MediaStream::ApplyTrackDisabling(TrackID aTrackID, MediaSegment* aSegment, Media
   }
 }
 
+void
+MediaStream::AddMainThreadListener(MainThreadMediaStreamListener* aListener)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aListener);
+  MOZ_ASSERT(!mMainThreadListeners.Contains(aListener));
+
+  mMainThreadListeners.AppendElement(aListener);
+
+  // If we have to send the notification or we have a runnable that will do it,
+  // let finish here.
+  if (!mFinishedNotificationSent || mNotificationMainThreadRunnable) {
+    return;
+  }
+
+  class NotifyRunnable final : public nsRunnable
+  {
+  public:
+    NotifyRunnable(MediaStream* aStream)
+      : mStream(aStream)
+    {}
+
+    NS_IMETHOD Run() override
+    {
+      MOZ_ASSERT(NS_IsMainThread());
+      mStream->mNotificationMainThreadRunnable = nullptr;
+      mStream->NotifyMainThreadListeners();
+      return NS_OK;
+    }
+
+  private:
+    ~NotifyRunnable() {}
+
+    nsRefPtr<MediaStream> mStream;
+  };
+
+  nsRefPtr<nsRunnable> runnable = new NotifyRunnable(this);
+  if (NS_WARN_IF(NS_FAILED(NS_DispatchToMainThread(runnable)))) {
+    return;
+  }
+
+  mNotificationMainThreadRunnable = runnable;
+}
+
 void
 SourceMediaStream::DestroyImpl()
 {

dom/media/MediaStreamGraph.h

@@ -373,20 +373,19 @@ public:
   // A disabled track has video replaced by black, and audio replaced by
   // silence.
   void SetTrackEnabled(TrackID aTrackID, bool aEnabled);
-  // Events will be dispatched by calling methods of aListener. It is the
+
+  // Finish event will be notified by calling methods of aListener. It is the
   // responsibility of the caller to remove aListener before it is destroyed.
-  void AddMainThreadListener(MainThreadMediaStreamListener* aListener)
-  {
-    NS_ASSERTION(NS_IsMainThread(), "Call only on main thread");
-    mMainThreadListeners.AppendElement(aListener);
-  }
+  void AddMainThreadListener(MainThreadMediaStreamListener* aListener);
   // It's safe to call this even if aListener is not currently a listener;
   // the call will be ignored.
   void RemoveMainThreadListener(MainThreadMediaStreamListener* aListener)
   {
-    NS_ASSERTION(NS_IsMainThread(), "Call only on main thread");
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(aListener);
     mMainThreadListeners.RemoveElement(aListener);
   }
+
   /**
    * Ensure a runnable will run on the main thread after running all pending
    * updates that were sent from the graph thread or will be sent before the
@@ -597,6 +596,16 @@ protected:
     mBuffer.ForgetUpTo(aCurrentTime - mBufferStartTime);
   }
 
+  void NotifyMainThreadListeners()
+  {
+    NS_ASSERTION(NS_IsMainThread(), "Call only on main thread");
+
+    for (int32_t i = mMainThreadListeners.Length() - 1; i >= 0; --i) {
+      mMainThreadListeners[i]->NotifyMainThreadStreamFinished();
+    }
+    mMainThreadListeners.Clear();
+  }
+
   bool ShouldNotifyStreamFinished()
   {
     NS_ASSERTION(NS_IsMainThread(), "Call only on main thread");
@@ -636,6 +645,7 @@ protected:
   TimeVarying<GraphTime,uint32_t,0> mExplicitBlockerCount;
   nsTArray<nsRefPtr<MediaStreamListener> > mListeners;
   nsTArray<MainThreadMediaStreamListener*> mMainThreadListeners;
+  nsRefPtr<nsRunnable> mNotificationMainThreadRunnable;
   nsTArray<TrackID> mDisabledTrackIDs;
 
   // Precomputed blocking status (over GraphTime).