Implement MediaStreamTrack contentHint skeleton.

content/public/renderer/media_stream_sink.h

 // 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.
 
 #ifndef CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_SINK_H_
 #define CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_SINK_H_
 
 #include "base/compiler_specific.h"
 #include "content/common/content_export.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
+#include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
 
 namespace content {
 
 // MediaStreamSink is the base interface for MediaStreamAudioSink and
 // MediaStreamVideoSink. It allows an implementation to receive notifications
 // about state changes on a blink::WebMediaStreamSource object or such an
 // object underlying a blink::WebMediaStreamTrack.
 class CONTENT_EXPORT MediaStreamSink {
  public:
   virtual void OnReadyStateChanged(
       blink::WebMediaStreamSource::ReadyState state) {}
   virtual void OnEnabledChanged(bool enabled) {}
+  virtual void OnContentHintChanged(
+      blink::WebMediaStreamTrack::ContentHintType content_hint) {}
 
  protected:
   virtual ~MediaStreamSink() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_SINK_H_