Allow muting/unmuting audio through media track API

media/base/renderer.h

Index: media/base/renderer.h
diff --git a/media/base/renderer.h b/media/base/renderer.h
index 89e349a9350d1c44564690a84bdc2391589e78d2..458266bdee675122673ad1101bea7e538222c3a5 100644
--- a/media/base/renderer.h
+++ b/media/base/renderer.h
@@ -16,6 +16,7 @@
 
 namespace media {
 
+class DemuxerStream;
 class DemuxerStreamProvider;
 class VideoFrame;
 
@@ -77,6 +78,15 @@ class MEDIA_EXPORT Renderer {
   // Returns whether |this| renders video.
   virtual bool HasVideo() = 0;
 
+  // Notifies renderer that the set of enabled audio streams/tracks has changed.

[wolenetz, 2016/03/30 00:31:32]

|enabledAudioStreams| can be an empty vector, which means no audio is enabled,
right? If so, please add to comment here like you already have in the video
method.

[servolk, 2016/03/30 01:13:12]

Done.

+  virtual void OnEnabledAudioStreamsChanged(
+      const std::vector<const DemuxerStream*>& enabledAudioStreams) {}
+
+  // Notifies renderer that the selected video stream has changed. The input
+  // parameter |selectedVideoStream| can be null, which means video is disabled.
+  virtual void OnSelectedVideoStreamChanged(
+      const DemuxerStream* selectedVideoStream) {}
+
  private:
   DISALLOW_COPY_AND_ASSIGN(Renderer);
 };