Update VideoFrameBuffer-related methods to not use references to scoped_refptr.

webrtc/common_video/video_frame.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 45 matching lines @@
 }
 
 int VideoFrame::height() const {
   return video_frame_buffer_ ? video_frame_buffer_->height() : 0;
 }
 
 bool VideoFrame::IsZeroSize() const {
   return !video_frame_buffer_;
 }
 
-const rtc::scoped_refptr<VideoFrameBuffer>& VideoFrame::video_frame_buffer()
-    const {
+rtc::scoped_refptr<VideoFrameBuffer> VideoFrame::video_frame_buffer() const {
   return video_frame_buffer_;
 }
 
 size_t EncodedImage::GetBufferPaddingBytes(VideoCodecType codec_type) {
   switch (codec_type) {
     case kVideoCodecVP8:
     case kVideoCodecVP9:
       return 0;
     case kVideoCodecH264:
       return kBufferPaddingBytesH264;
     case kVideoCodecI420:
     case kVideoCodecRED:
     case kVideoCodecULPFEC:
     case kVideoCodecFlexfec:
     case kVideoCodecGeneric:
     case kVideoCodecUnknown:
       return 0;
   }
   RTC_NOTREACHED();
   return 0;
 }
 
 }  // namespace webrtc