Revert of MediaStream audio object graph untangling and clean-ups.

content/public/renderer/media_stream_audio_sink.cc

 // 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/media_stream_audio_track.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
 
 namespace content {
 
 void MediaStreamAudioSink::AddToAudioTrack(
     MediaStreamAudioSink* sink,
     const blink::WebMediaStreamTrack& track) {
   DCHECK(track.source().getType() == blink::WebMediaStreamSource::TypeAudio);
-  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::From(track);
-  DCHECK(native_track);
+  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::GetTrack(track);
   native_track->AddSink(sink);
 }
 
 void MediaStreamAudioSink::RemoveFromAudioTrack(
     MediaStreamAudioSink* sink,
     const blink::WebMediaStreamTrack& track) {
-  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::From(track);
-  DCHECK(native_track);
+  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::GetTrack(track);
   native_track->RemoveSink(sink);
 }
 
 media::AudioParameters MediaStreamAudioSink::GetFormatFromAudioTrack(
     const blink::WebMediaStreamTrack& track) {
-  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::From(track);
-  DCHECK(native_track);
+  MediaStreamAudioTrack* native_track = MediaStreamAudioTrack::GetTrack(track);
   return native_track->GetOutputFormat();
 }
 
 }  // namespace content