Add video frame refresh to MediaStream and VideoCapture stacks.

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 <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 194 matching lines @@
   track.setExtraData(new MediaStreamVideoTrack(source,
                                                constraints,
                                                callback,
                                                enabled));
   return track;
 }
 
 // static
 MediaStreamVideoTrack* MediaStreamVideoTrack::GetVideoTrack(
      const blink::WebMediaStreamTrack& track) {
+  if (track.isNull() ||
+      track.source().getType() != blink::WebMediaStreamSource::TypeVideo) {
+    return nullptr;
+  }
   return static_cast<MediaStreamVideoTrack*>(track.getExtraData());
 }
 
 MediaStreamVideoTrack::MediaStreamVideoTrack(
     MediaStreamVideoSource* source,
     const blink::WebMediaConstraints& constraints,
     const MediaStreamVideoSource::ConstraintsCallback& callback,
     bool enabled)
     : MediaStreamTrack(true),
       frame_deliverer_(
           new MediaStreamVideoTrack::FrameDeliverer(source->io_task_runner(),
                                                     enabled)),
       constraints_(constraints),
       source_(source) {
   DCHECK(!constraints.isNull());
   source->AddTrack(this,
                    base::Bind(
                        &MediaStreamVideoTrack::FrameDeliverer::DeliverFrameOnIO,
                        frame_deliverer_),
                    constraints, callback);
 }
 
 MediaStreamVideoTrack::~MediaStreamVideoTrack() {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
+
+  // It's critical to check that |sinks_| is empty because a
+  // MediaStreamVideoSink holds a pointer to this track until it calls
+  // RemoveSink().

[mcasas, 2016/04/05 23:12:52]

This is true and unfortunately so because the
ownership happens to go via Blink. With the 
Onion Soup project, however, these classes will 
migrate to Blink side and they'll become garbage 
collected, so again these ownership graphs will
need revisit.

[miu, 2016/04/06 00:03:18]

FYI--Your comment here makes me wonder if this change is conflicting w/ other
current efforts: https://codereview.chromium.org/1834323002/  If that change
lands in the next 2-3 weeks, am I good?  ;-)

   DCHECK(sinks_.empty());
+
   Stop();
   DVLOG(3) << "~MediaStreamVideoTrack()";
 }
 
 void MediaStreamVideoTrack::AddSink(
     MediaStreamVideoSink* sink, const VideoCaptureDeliverFrameCB& callback) {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   DCHECK(std::find(sinks_.begin(), sinks_.end(), sink) == sinks_.end());
   sinks_.push_back(sink);
   frame_deliverer_->AddCallback(sink, callback);
+
   // Request source to deliver a frame because a new sink is added.
-  if (source_)
-    source_->RequestRefreshFrame();
+  RequestRefreshFrame();
 }
 
 void MediaStreamVideoTrack::RemoveSink(MediaStreamVideoSink* sink) {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   std::vector<MediaStreamVideoSink*>::iterator it =
       std::find(sinks_.begin(), sinks_.end(), sink);
   DCHECK(it != sinks_.end());
   sinks_.erase(it);
   frame_deliverer_->RemoveCallback(sink);
 }
@@ skipping 14 matching lines @@
   OnReadyStateChanged(blink::WebMediaStreamSource::ReadyStateEnded);
 }
 
 void MediaStreamVideoTrack::OnReadyStateChanged(
     blink::WebMediaStreamSource::ReadyState state) {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   for (auto* sink : sinks_)
     sink->OnReadyStateChanged(state);
 }
 
+void MediaStreamVideoTrack::RequestRefreshFrame() {
+  DCHECK(main_render_thread_checker_.CalledOnValidThread());
+  if (source_)
+    source_->RequestRefreshFrame();
+}
+
 }  // namespace content