Add separate base classes for I420 and I444 buffers

webrtc/api/video/i420_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.
  */
 #include "webrtc/api/video/i420_buffer.h"
@@ skipping 118 matching lines @@
       static_cast<libyuv::RotationMode>(rotation)));
 
   return buffer;
 }
 
 void I420Buffer::InitializeData() {
   memset(data_.get(), 0,
          I420DataSize(height_, stride_y_, stride_u_, stride_v_));
 }
 
-VideoFrameBuffer::Type I420Buffer::type() const {
-  return Type::kI420;
-}
-
 int I420Buffer::width() const {
   return width_;
 }
 
 int I420Buffer::height() const {
   return height_;
 }
 
 const uint8_t* I420Buffer::DataY() const {
   return data_.get();
@@ skipping 82 matching lines @@
       src,
       (src.width() - crop_width) / 2, (src.height() - crop_height) / 2,
       crop_width, crop_height);
 }
 
 void I420Buffer::ScaleFrom(const VideoFrameBuffer& src) {
   CropAndScaleFrom(src, 0, 0, src.width(), src.height());
 }
 
 }  // namespace webrtc