New method I420Buffer::Copy.

webrtc/common_video/include/video_frame_buffer.h

Index: webrtc/common_video/include/video_frame_buffer.h
diff --git a/webrtc/common_video/include/video_frame_buffer.h b/webrtc/common_video/include/video_frame_buffer.h
index 270f2d5a2d036b20f09fff61bc3bdba160b7b8e0..4fd68c5780cd2d5c52a38338e4e4591bf494f5ca 100644
--- a/webrtc/common_video/include/video_frame_buffer.h
+++ b/webrtc/common_video/include/video_frame_buffer.h
@@ -81,6 +81,8 @@ class I420Buffer : public VideoFrameBuffer {
   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;