Allow muting/unmuting audio through media track API

media/base/renderer.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BASE_RENDERER_H_
 #define MEDIA_BASE_RENDERER_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "media/base/buffering_state.h"
 #include "media/base/cdm_context.h"
 #include "media/base/media_export.h"
 #include "media/base/pipeline_status.h"
 
 namespace media {
 
+class DemuxerStream;
 class DemuxerStreamProvider;
 class VideoFrame;
 
 class MEDIA_EXPORT Renderer {
  public:
   Renderer();
 
   // Stops rendering and fires any pending callbacks.
   virtual ~Renderer();
 
@@ skipping 41 matching lines @@
 
   // Returns the current media time.
   virtual base::TimeDelta GetMediaTime() = 0;
 
   // Returns whether |this| renders audio.
   virtual bool HasAudio() = 0;
 
   // 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);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_RENDERER_H_