Update I420Buffer to new VideoFrameBuffer interface

webrtc/api/video/video_frame_buffer.h

Index: webrtc/api/video/video_frame_buffer.h
diff --git a/webrtc/api/video/video_frame_buffer.h b/webrtc/api/video/video_frame_buffer.h
index 13005afc8a57b5370e3fce5bd88717e51e970f66..fa711d85e1b368873ccf69b8c9e3b094ec6948da 100644
--- a/webrtc/api/video/video_frame_buffer.h
+++ b/webrtc/api/video/video_frame_buffer.h
@@ -63,8 +63,12 @@ class VideoFrameBuffer : public rtc::RefCountInterface {
 
   // These functions should only be called if type() is of the correct type.
   // Calling with a different type will result in a crash.
+  // TODO(magjed): Return raw pointers for GetI420 once deprecated interface is
+  // removed.
   rtc::scoped_refptr<I420BufferInterface> GetI420();
-  rtc::scoped_refptr<I444BufferInterface> GetI444();
+  rtc::scoped_refptr<const I420BufferInterface> GetI420() const;
+  I444BufferInterface* GetI444();
+  const I444BufferInterface* GetI444() const;
 
   // Deprecated - use ToI420() first instead.
   // Returns pointer to the pixel data for a given plane. The memory is owned by