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

media/cast/sender/video_encoder.cc

 // Copyright 2014 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 "media/cast/net/pacing/mock_paced_packet_sender.h"
+#include "media/cast/sender/video_encoder.h"
+#include "media/cast/sender/video_frame_factory.h"
 
 namespace media {
 namespace cast {
 
-MockPacedPacketSender::MockPacedPacketSender() {}
-
-MockPacedPacketSender::~MockPacedPacketSender() {}
+scoped_ptr<VideoFrameFactory> VideoEncoder::CreateVideoFrameFactory() {
+  return nullptr;
+}
 
 }  // namespace cast
 }  // namespace media