Set audio format before adding pepper sink to audio track.

content/public/renderer/media_stream_audio_sink.h

 // Copyright 2013 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 CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_AUDIO_SINK_H_
 #define CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_AUDIO_SINK_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 19 matching lines @@
   // Called on the main render thread.
   static void AddToAudioTrack(MediaStreamAudioSink* sink,
                               const blink::WebMediaStreamTrack& track);
 
   // Removes a MediaStreamAudioSink from the audio track to stop receiving
   // audio data from the track.
   // Called on the main render thread.
   static void RemoveFromAudioTrack(MediaStreamAudioSink* sink,
                                    const blink::WebMediaStreamTrack& track);
 
+  // Returns the format of the audio track.
+  // Called on the main render thread.
+  static const media::AudioParameters& GetFormatFromAudioTrack(
+      const blink::WebMediaStreamTrack& track);
+
   // Callback called to deliver audio data. The data in |audio_bus| respects the
   // AudioParameters passed in the last call to OnSetFormat().  Called on
   // real-time audio thread.
   //
   // |estimated_capture_time| is the local time at which the first sample frame
   // in |audio_bus| either: 1) was generated, if it was done so locally; or 2)
   // should be targeted for play-out, if it was generated from a remote
   // source. Either way, an implementation should not play-out the audio before
   // this point-in-time. This value is NOT a high-resolution timestamp, and so
   // it should not be used as a presentation time; but, instead, it should be
   // used for buffering playback and for A/V synchronization purposes.
   virtual void OnData(const media::AudioBus& audio_bus,
                       base::TimeTicks estimated_capture_time) = 0;
 
   // Callback called when the format of the audio stream has changed.  This is
   // always called at least once before OnData(), and on the same thread.
   virtual void OnSetFormat(const media::AudioParameters& params) = 0;
 
  protected:
   ~MediaStreamAudioSink() override {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_AUDIO_SINK_H_