MediaStream audio sourcing: Bypass audio processing for non-WebRTC cases.

content/renderer/media/media_stream_audio_track.h

Index: content/renderer/media/media_stream_audio_track.h
diff --git a/content/renderer/media/media_stream_audio_track.h b/content/renderer/media/media_stream_audio_track.h
index 2175b4e186f47fefc982e097a1691dac1fdd7383..c4b6517590d689222f7b011623da4fc2b81913f9 100644
--- a/content/renderer/media/media_stream_audio_track.h
+++ b/content/renderer/media/media_stream_audio_track.h
@@ -33,7 +33,8 @@ class CONTENT_EXPORT MediaStreamAudioTrack : public MediaStreamTrack {
   // Called on the main render thread.
   virtual void RemoveSink(MediaStreamAudioSink* sink) = 0;
 
-  // TODO(tommi, xians): Remove this method.
+  // NOTE: This can return null if the WebRTC audio pipeline is not being used.
+  // TODO(tommi, xians): Remove this method.  http://crbug.com/577874
   virtual webrtc::AudioTrackInterface* GetAudioAdapter();
 
   // Returns the output format of the capture source. May return an invalid
@@ -42,6 +43,7 @@ class CONTENT_EXPORT MediaStreamAudioTrack : public MediaStreamTrack {
   // TODO(tommi): This method appears to only be used by Pepper and in fact
   // does not appear to be necessary there.  We should remove it since it adds
   // to the complexity of all types of audio tracks+source implementations.
+  // http://crbug.com/577874
   virtual media::AudioParameters GetOutputFormat() const = 0;
 
  private: