Reland of Move MutableDataY{,U,V} methods to I420Buffer only.

webrtc/common_video/video_frame_buffer.cc

 /*
  *  Copyright (c) 2015 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 13 matching lines @@
 namespace webrtc {
 
 namespace {
 
 int I420DataSize(int height, int stride_y, int stride_u, int stride_v) {
   return stride_y * height + (stride_u + stride_v) * ((height + 1) / 2);
 }
 
 }  // namespace
 
-uint8_t* VideoFrameBuffer::MutableDataY() {
-  RTC_NOTREACHED();
-  return nullptr;
-}
-uint8_t* VideoFrameBuffer::MutableDataU() {
-  RTC_NOTREACHED();
-  return nullptr;
-}
-uint8_t* VideoFrameBuffer::MutableDataV() {
-  RTC_NOTREACHED();
-  return nullptr;
-}
-
 VideoFrameBuffer::~VideoFrameBuffer() {}
 
 I420Buffer::I420Buffer(int width, int height)
     : I420Buffer(width, height, width, (width + 1) / 2, (width + 1) / 2) {
 }
 
 I420Buffer::I420Buffer(int width,
                        int height,
                        int stride_y,
                        int stride_u,
@@ skipping 317 matching lines @@
 void* WrappedI420Buffer::native_handle() const {
   return nullptr;
 }
 
 rtc::scoped_refptr<VideoFrameBuffer> WrappedI420Buffer::NativeToI420Buffer() {
   RTC_NOTREACHED();
   return nullptr;
 }
 
 }  // namespace webrtc