[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..ae944b6203dc08dc6e5faa5f3842f27c52648504 100644
--- a/media/cast/sender/video_sender.h
+++ b/media/cast/sender/video_sender.h
@@ -15,6 +15,7 @@
 #include "media/cast/cast_config.h"
 #include "media/cast/sender/congestion_control.h"
 #include "media/cast/sender/frame_sender.h"
+#include "media/cast/sender/video_frame_factory.h"
 
 namespace media {
 
@@ -56,6 +57,13 @@ class VideoSender : public FrameSender,
   void InsertRawVideoFrame(const scoped_refptr<media::VideoFrame>& video_frame,
                            const base::TimeTicks& reference_time);
 
+  // Returns a |VideoFrameFactory| that can be used to create
+  // |media::VideoFrame| objects with potentially better affinity with the
+  // encoder.
+  scoped_refptr<VideoFrameFactory> video_frame_factory() {
+    return video_frame_factory_;
+  }
+
  protected:
   int GetNumberOfFramesInEncoder() const override;
   base::TimeDelta GetInFlightMediaDuration() const override;
@@ -76,6 +84,10 @@ class VideoSender : public FrameSender,
   // a hardware-based encoder.
   scoped_ptr<VideoEncoder> video_encoder_;
 
+  // Provides |media::VideoFrame| objects suitable for encoding. The encoder may
+  // provide a specialized instance, otherwise a default implementation is used.
+  scoped_refptr<VideoFrameFactory> video_frame_factory_;
+
   // The number of frames queued for encoding, but not yet sent.
   int frames_in_encoder_;