Add generic interfaces for the sinks of the media stream audio track

content/public/renderer/media_stream_audio_sink.cc

Index: content/public/renderer/media_stream_audio_sink.cc
diff --git a/content/public/renderer/media_stream_audio_sink.cc b/content/public/renderer/media_stream_audio_sink.cc
new file mode 100644
index 0000000000000000000000000000000000000000..deb845f5aa403bce6f6d741f021216fd960c19bd
--- /dev/null
+++ b/content/public/renderer/media_stream_audio_sink.cc
@@ -0,0 +1,29 @@
+// 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.
+
+#include "content/public/renderer/media_stream_audio_sink.h"
+
+#include "base/logging.h"
+#include "content/renderer/media/webrtc_local_audio_track.h"
+#include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
+
+namespace content {
+
+void MediaStreamVideoSink::AddToAudioTrack(
+    MediaStreamAudioSink* sink, const blink::WebMediaStreamTrack& track) {
+  DCHECK(track.source().type() == blink::WebMediaStreamSource::TypeAudio);
+  WebRtcLocalAudioTrack* audio_track =
+      static_cast <WebRtcLocalAudioTrack*>(track.extraData());
+  audio_track->AddSink(sink);
+}
+
+void MediaStreamVideoSink::RemoveFromTrack(
+    MediaStreamAudioSink* sink,
+    const blink::WebMediaStreamTrack& track) {
+  WebRtcLocalAudioTrack* audio_track =
+      static_cast <WebRtcLocalAudioTrack*>(track.extraData());
+  audio_track->RemoveSink(sink);
+}
+
+}  // namespace content