Add VideoTrackSink interface to content/public

content/renderer/media/media_stream_video_track.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/renderer/media/media_stream_video_track.h"
+
+#include "content/renderer/media/webrtc/webrtc_video_sink_adapter.h"
+
+namespace content {
+
+// Wrapper which allows to use std::find_if() when adding and removing
+// sinks to/from |sinks_|.
+struct SinkWrapper {
+  explicit SinkWrapper(MediaStreamVideoSink* sink) : sink_(sink) {}
+  bool operator()(
+      const WebRtcVideoSinkAdapter* owner) {
+    return owner->sink() == sink_;
+  }
+  MediaStreamVideoSink* sink_;
+};
+
+MediaStreamVideoTrack::MediaStreamVideoTrack(webrtc::VideoTrackInterface* track)
+    : MediaStreamTrackExtraData(track),
+      video_track_(track) {
+}
+
+MediaStreamVideoTrack::~MediaStreamVideoTrack() {
+  DCHECK(sinks_.empty());
+}
+
+void MediaStreamVideoTrack::AddSink(MediaStreamVideoSink* sink) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(std::find_if(sinks_.begin(), sinks_.end(),
+                      SinkWrapper(sink)) == sinks_.end());
+  sinks_.push_back(new WebRtcVideoSinkAdapter(video_track_, sink));
+}
+
+void MediaStreamVideoTrack::RemoveSink(MediaStreamVideoSink* sink) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  ScopedVector<WebRtcVideoSinkAdapter>::iterator it =
+      std::find_if(sinks_.begin(), sinks_.end(), SinkWrapper(sink));
+  DCHECK(it != sinks_.end());
+  sinks_.erase(it);

[no longer working on chromium, 2013/11/28 15:20:46]

To be more specific on the racing concern, I think you need to have a Reset()
method on WebRtcVideoSinkAdapter, before you call  sinks_.erase(it), you need to
call it->Reset() to set the sink_ to NULL in WebRtcVideoSinkAdapter

[perkj_chrome, 2013/11/29 13:29:48]

Why would I need that? sinks_ is a scoped_vector ? WebRtcVideoSinkAdapter is not
ref counted.

+}
+
+}  // namespace content