[Cast] VideoFrameFactory interface to vend frames with encoder affinity.

media/cast/sender/video_sender.h

Index: media/cast/sender/video_sender.h
diff --git a/media/cast/sender/video_sender.h b/media/cast/sender/video_sender.h
index 826099ecf4dc728f31f57e954fc057fc196aa277..506700d6c711df6cb8f6ee3c4d178f63804d6e77 100644
--- a/media/cast/sender/video_sender.h
+++ b/media/cast/sender/video_sender.h
@@ -24,6 +24,7 @@ namespace cast {
 
 class CastTransportSender;
 class VideoEncoder;
+class VideoFrameFactory;
 
 typedef base::Callback<void(base::TimeDelta)> PlayoutDelayChangeCB;
 
@@ -56,6 +57,11 @@ class VideoSender : public FrameSender,
   void InsertRawVideoFrame(const scoped_refptr<media::VideoFrame>& video_frame,
                            const base::TimeTicks& reference_time);
 
+  // Creates a |VideoFrameFactory| object to vend |VideoFrame| object with
+  // encoder affinity (defined as offering some sort of performance benefit). If
+  // the encoder does not have any such capability, returns null.
+  scoped_ptr<VideoFrameFactory> CreateVideoFrameFactory();
+
  protected:
   int GetNumberOfFramesInEncoder() const override;
   base::TimeDelta GetInFlightMediaDuration() const override;