Add support for unmixed audio from remote WebRTC remote tracks.

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
index 507bef0fa29c9e6cdb623e5fbc7f7ce8d497cc3f..a6e01a9c7cf47800d30843dcfee8d2e8a0bef984 100644
--- a/content/public/renderer/media_stream_audio_sink.cc
+++ b/content/public/renderer/media_stream_audio_sink.cc
@@ -5,8 +5,7 @@
 #include "content/public/renderer/media_stream_audio_sink.h"
 
 #include "base/logging.h"
-#include "content/renderer/media/media_stream_track.h"
-#include "content/renderer/media/webrtc_local_audio_track.h"
+#include "content/renderer/media/media_stream_audio_track.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
 
@@ -16,44 +15,21 @@ void MediaStreamAudioSink::AddToAudioTrack(
     MediaStreamAudioSink* sink,
     const blink::WebMediaStreamTrack& track) {
   DCHECK(track.source().type() == blink::WebMediaStreamSource::TypeAudio);
-  MediaStreamTrack* native_track = MediaStreamTrack::GetTrack(track);
-  // TODO(xians): Support remote audio track.
-  if (!native_track->is_local_track()) {
-    LOG(ERROR) << "Can't add the sink to a remote audio track";
-    return;
-  }
-
-  WebRtcLocalAudioTrack* audio_track =
-      static_cast<WebRtcLocalAudioTrack*>(native_track);
-  audio_track->AddSink(sink);
+  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::GetTrack(track);
+  native_track->AddSink(sink);
 }
 
 void MediaStreamAudioSink::RemoveFromAudioTrack(
     MediaStreamAudioSink* sink,
     const blink::WebMediaStreamTrack& track) {
-  MediaStreamTrack* native_track = MediaStreamTrack::GetTrack(track);
-  // TODO(xians): Support remote audio track.
-  if (!native_track->is_local_track()) {
-    LOG(ERROR) << "Can't remove the sink from a remote audio track";
-    return;
-  }
-
-  WebRtcLocalAudioTrack* audio_track =
-      static_cast<WebRtcLocalAudioTrack*>(native_track);
-  audio_track->RemoveSink(sink);
+  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::GetTrack(track);
+  native_track->RemoveSink(sink);
 }
 
 media::AudioParameters MediaStreamAudioSink::GetFormatFromAudioTrack(
     const blink::WebMediaStreamTrack& track) {
-  MediaStreamTrack* native_track = MediaStreamTrack::GetTrack(track);
-  if (!native_track->is_local_track()) {
-    LOG(ERROR) << "Can't get format from a remote audio track";
-    return media::AudioParameters();
-  }
-
-  WebRtcLocalAudioTrack* audio_track =
-      static_cast<WebRtcLocalAudioTrack*>(native_track);
-  return audio_track->GetOutputFormat();
+  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::GetTrack(track);
+  return native_track->GetOutputFormat();
 }
 
 }  // namespace content