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

webrtc/api/androidvideotracksource.cc

 /*
  *  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.
  */
 
@@ skipping 97 matching lines @@
 
   int rotated_width = crop_width;
   int rotated_height = crop_height;
 
   rtc::CritScope lock(&apply_rotation_crit_);
   if (apply_rotation_ && (rotation == 90 || rotation == 270)) {
     std::swap(adapted_width, adapted_height);
     std::swap(rotated_width, rotated_height);
   }
 
-  rtc::scoped_refptr<webrtc::VideoFrameBuffer> buffer =
+  rtc::scoped_refptr<webrtc::I420Buffer> buffer =
       pre_scale_pool_.CreateBuffer(rotated_width, rotated_height);
 
   const uint8_t* y_plane = static_cast<const uint8_t*>(frame_data);
   const uint8_t* uv_plane = y_plane + width * height;
   int uv_width = (width + 1) / 2;
 
   RTC_CHECK_GE(length, width * height + 2 * uv_width * ((height + 1) / 2));
 
   // Can only crop at even pixels.
   crop_x &= ~1;
@@ skipping 124 matching lines @@
   }
   *crop_x = (width - *crop_width) / 2;
   *crop_y = (height - *crop_height) / 2;
 
   *translated_camera_time_us = timestamp_aligner_.ClipTimestamp(
       camera_time_us + offset_us, system_time_us);
   return true;
 }
 
 }  // namespace webrtc