New method I420Buffer::Copy.

webrtc/common_video/include/video_frame_buffer.h

 /*
  *  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 63 matching lines @@
   int width() const override;
   int height() const override;
   const uint8_t* data(PlaneType type) const override;
   // Non-const data access is only allowed if HasOneRef() is true to protect
   // against unexpected overwrites.
   uint8_t* MutableData(PlaneType type) override;
   int stride(PlaneType type) const override;
   void* native_handle() const override;
   rtc::scoped_refptr<VideoFrameBuffer> NativeToI420Buffer() override;
 
+  virtual rtc::scoped_refptr<I420Buffer> Copy();

[perkj_webrtc, 2016/03/23 14:38:09]

Can we move this to be a helper method. ie. Move to below ShalloCenterCrop. 
Call it  rtc::scoped_refptr<VideoFrameBuffer> CopyI420Buffer(const
rtc::scoped_refptr<I420Buffer>& buffer);

[nisse-webrtc, 2016/03/24 12:52:52]

For my intended usecase, it's desirable that the return value is an I420Buffer. 

[perkj_webrtc, 2016/03/24 13:18:42]

that is fine. But add a helper function instead of a memeber method? 

+
  protected:
   ~I420Buffer() override;
 
  private:
   const int width_;
   const int height_;
   const int stride_y_;
   const int stride_u_;
   const int stride_v_;
   const std::unique_ptr<uint8_t, AlignedFreeDeleter> data_;
@@ skipping 58 matching lines @@
 // Helper function to crop |buffer| without making a deep copy. May only be used
 // for non-native frames.
 rtc::scoped_refptr<VideoFrameBuffer> ShallowCenterCrop(
     const rtc::scoped_refptr<VideoFrameBuffer>& buffer,
     int cropped_width,
     int cropped_height);
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_COMMON_VIDEO_INCLUDE_VIDEO_FRAME_BUFFER_H_