Add support for unmixed audio from remote WebRTC remote tracks.

content/renderer/media/media_stream_track.cc

Index: content/renderer/media/media_stream_track.cc
diff --git a/content/renderer/media/media_stream_track.cc b/content/renderer/media/media_stream_track.cc
index 70ebca194cc27d80e6016dc4eece417e3746b99b..7992e237f832a6824a3ea43b99900248ea8220cc 100644
--- a/content/renderer/media/media_stream_track.cc
+++ b/content/renderer/media/media_stream_track.cc
@@ -4,18 +4,13 @@
 
 #include "content/renderer/media/media_stream_track.h"
 
-#include "base/logging.h"
-#include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
-#include "third_party/libjingle/source/talk/app/webrtc/mediastreaminterface.h"
-
 namespace content {
 
 // static
 MediaStreamTrack* MediaStreamTrack::GetTrack(
     const blink::WebMediaStreamTrack& track) {
-  if (track.isNull())
-    return NULL;
-  return static_cast<MediaStreamTrack*>(track.extraData());
+  return track.isNull() ?
+      nullptr : static_cast<MediaStreamTrack*>(track.extraData());
 }
 
 MediaStreamTrack::MediaStreamTrack(bool is_local_track)
@@ -25,9 +20,4 @@ MediaStreamTrack::MediaStreamTrack(bool is_local_track)
 MediaStreamTrack::~MediaStreamTrack() {
 }
 
-webrtc::AudioTrackInterface* MediaStreamTrack::GetAudioAdapter() {
-  NOTREACHED();
-  return nullptr;
-}
-
 }  // namespace content