Add VideoTrackSink interface to content/public

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"
+
+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 MediaStreamSink {
+ public:
+  virtual void OnReadyStateChanged(
+      blink::WebMediaStreamSource::ReadyState state) {}
+
+ protected:
+  virtual ~MediaStreamSink() {}
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_SINK_H_