VideoTrackAdapter: Add passing frames monitor, notify MSVCS -> MSVTrack(s)

content/renderer/media/media_stream_track.h

Index: content/renderer/media/media_stream_track.h
diff --git a/content/renderer/media/media_stream_track.h b/content/renderer/media/media_stream_track.h
index 456005d4d054284e2a999187c5375c171a468369..3492a062b89d59c23a297159afb88a6259e1e88a 100644
--- a/content/renderer/media/media_stream_track.h
+++ b/content/renderer/media/media_stream_track.h
@@ -34,6 +34,8 @@ class CONTENT_EXPORT MediaStreamTrack
   // If a subclass overrides this method it has to call the base class.
   virtual void SetEnabled(bool enabled);
 
+  virtual void SetMutedState(bool muted_state);
+
   // TODO(xians): Make this pure virtual when Stop[Track] has been
   // implemented for remote audio tracks.
   virtual void Stop();
@@ -45,6 +47,9 @@ class CONTENT_EXPORT MediaStreamTrack
  protected:
   scoped_refptr<webrtc::MediaStreamTrackInterface> track_;
 
+  // Set to true if the owner MediaStreamSource is not delivering frames.
+  bool muted_state_;
+
  private:
   const bool is_local_track_;