Bug 1238906 - part2 : notify audible state from MDSM to ME. r=jwwang

dom/html/HTMLMediaElement.h

@@ -397,6 +397,9 @@ public:
   // when the connection between Rtsp server and client gets lost.
   virtual void ResetConnectionState() final override;
 
+  // Called by media decoder when the audible state changed.
+  virtual void NotifyAudibleStateChanged(bool aAudible) final override;
+
   // XPCOM GetPreload() is OK
   void SetPreload(const nsAString& aValue, ErrorResult& aRv)
   {
@@ -1525,6 +1528,9 @@ private:
   // initially be set to zero seconds. This time is used to allow the element to
   // be seeked even before the media is loaded.
   double mDefaultPlaybackStartPosition;
+
+  // True if the audio track is producing audible sound.
+  bool mIsAudioTrackAudible;
 };
 
 } // namespace dom