Add support for unmixed audio from remote WebRTC remote tracks.

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
new file mode 100644
index 0000000000000000000000000000000000000000..8a80bc10bcf1c5c8781ebb738c88bc14ee14da38
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+++ b/content/renderer/media/media_stream_audio_track.h
@@ -0,0 +1,49 @@
+// Copyright 2015 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_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_TRACK_H_
+#define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_TRACK_H_
+
+#include "content/renderer/media/media_stream_track.h"
+
+namespace webrtc {
+class AudioTrackInterface;
+}  // namespace webrtc
+
+namespace content {
+
+class MediaStreamAudioSink;
+
+class CONTENT_EXPORT MediaStreamAudioTrack : public MediaStreamTrack {
+ public:
+  explicit MediaStreamAudioTrack(bool is_local_track);
+  ~MediaStreamAudioTrack() override;
+
+  static MediaStreamAudioTrack* GetTrack(
+      const blink::WebMediaStreamTrack& track);
+
+  // Add a sink to the track. This function will trigger a OnSetFormat()
+  // call on the |sink|.
+  // Called on the main render thread.
+  virtual void AddSink(MediaStreamAudioSink* sink) = 0;
+
+  // Remove a sink from the track.
+  // Called on the main render thread.
+  virtual void RemoveSink(MediaStreamAudioSink* sink) = 0;
+
+  // TODO(tommi, xians): Remove this method.
+  virtual webrtc::AudioTrackInterface* GetAudioAdapter();
+
+  // Returns the output format of the capture source. May return an invalid
+  // AudioParameters if the format is not yet available.
+  // Called on the main render thread.
+  virtual media::AudioParameters GetOutputFormat() const = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MediaStreamAudioTrack);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_TRACK_H_