Make WebRtcVideoChannel2::WebRtcVideoSendStream implement rtc::VideoRendererInterface.

webrtc/media/base/videosinkinterface.h

+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MEDIA_BASE_VIDEOSINKINTERFACE_H_
+#define WEBRTC_MEDIA_BASE_VIDEOSINKINTERFACE_H_
+
+namespace rtc {
+
+template <typename VideoFrameT>
+class VideoSinkInterface {
+ public:
+  virtual void OnFrame(const VideoFrameT& frame) = 0;
+
+ protected:
+  ~VideoSinkInterface() {}
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_MEDIA_BASE_VIDEOSINKINTERFACE_H_