Add video-rendering to mojo media pipeline.

media/renderers/video_renderer_impl.cc

Index: media/renderers/video_renderer_impl.cc
diff --git a/media/renderers/video_renderer_impl.cc b/media/renderers/video_renderer_impl.cc
index ab7d0795d5769c65466fee5bfdfc3989f242152c..5912c77f42713471ee21046c0c7245b0ce47fdc4 100644
--- a/media/renderers/video_renderer_impl.cc
+++ b/media/renderers/video_renderer_impl.cc
@@ -126,6 +126,7 @@ void VideoRendererImpl::Initialize(
     CdmContext* cdm_context,
     const StatisticsCB& statistics_cb,
     const BufferingStateCB& buffering_state_cb,
+    const NaturalSizeChangedCB& natural_size_changed_cb,
     const base::Closure& ended_cb,
     const PipelineStatusCB& error_cb,
     const TimeSource::WallClockTimeCB& wall_clock_time_cb,
@@ -158,7 +159,7 @@ void VideoRendererImpl::Initialize(
   // calls to OnTimeStateChanged() under lock, which can deadlock the compositor
   // and media threads.
   buffering_state_cb_ = BindToCurrentLoop(buffering_state_cb);
-
+  natural_size_changed_cb_ = natural_size_changed_cb;
   statistics_cb_ = statistics_cb;
   ended_cb_ = ended_cb;
   error_cb_ = error_cb;
@@ -244,6 +245,7 @@ scoped_refptr<VideoFrame> VideoRendererImpl::Render(
   task_runner_->PostTask(FROM_HERE, base::Bind(&VideoRendererImpl::AttemptRead,
                                                weak_factory_.GetWeakPtr()));
 
+  // TODO(alokp): Fire NaturalSizeChangedCB if necessary.

[xhwang, 2016/04/12 19:40:38]

This could be related to this comment:
https://code.google.com/p/chromium/codesearch#chromium/src/media/base/video_r...

There are multiple ways to do this:
1. As you proposed, move the natural size tracking logic to this class and fire
the callback here.
2. Keep the logic in VideoFrameCompositor, and pass a NaturalSizeChangedCB in
Start(), such that we only get notified when we are using the new rendering path
(with Start()/Stop). We won't get notified when we are using the old rendering
path.

Thinking more on this, maybe (1) makes more sense...

[alokp, 2016/04/19 00:16:08]

Done.

   return result;
 }