Add VideoTrackSink interface to content/public

content/public/renderer/media_stream_video_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_video_sink.h"
+
+#include "base/logging.h"
+#include "content/renderer/media/media_stream_video_track.h"
+#include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
+
+namespace content {
+
+void AddToVideoTrack(MediaStreamVideoSink* sink,
+                     const blink::WebMediaStreamTrack& track) {
+  DCHECK_EQ(blink::WebMediaStreamSource::TypeVideo, track.source().type());
+  MediaStreamVideoTrack* video_track =
+      static_cast<MediaStreamVideoTrack*>(track.extraData());
+  video_track->AddSink(sink);

[Alpha Left Google, 2013/12/02 17:44:37]

track.isNull() can be true and track.extraData() can also be NULL.

See:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

Since the caller doesn't guarantee adding the sink will be successful I think
it's best to handle error cases here and return a boolean.

[perkj_chrome, 2013/12/03 16:14:17]

I would argue that it is a programming error if track.isNull()==true or the
extra data don't exist. We create the extra data as soon as a
blink::WebMediaStreamTrack is created currently.
If this is not true, this will crash and we should fix it.

+}
+
+void RemoveFromVideoTrack(MediaStreamVideoSink* sink,
+                          const blink::WebMediaStreamTrack& track) {
+  DCHECK_EQ(blink::WebMediaStreamSource::TypeVideo, track.source().type());
+  MediaStreamVideoTrack* video_track =
+      static_cast<MediaStreamVideoTrack*>(track.extraData());
+  video_track->RemoveSink(sink);
+}
+
+}  // namespace content