Update I420Buffer to new VideoFrameBuffer interface

webrtc/api/video/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 45 matching lines @@
   virtual int height() const = 0;
 
   // Returns a memory-backed frame buffer in I420 format. If the pixel data is
   // in another format, a conversion will take place. All implementations must
   // provide a fallback to I420 for compatibility with e.g. the internal WebRTC
   // software encoders.
   virtual rtc::scoped_refptr<I420BufferInterface> ToI420();
 
   // 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
   // the VideoFrameBuffer object and must not be freed by the caller.
   virtual const uint8_t* DataY() const;
   virtual const uint8_t* DataU() const;
   virtual const uint8_t* DataV() const;
   // Returns the number of bytes between successive rows for a given plane.
   virtual int StrideY() const;
   virtual int StrideU() const;
@@ skipping 55 matching lines @@
 
   rtc::scoped_refptr<I420BufferInterface> ToI420() final;
 
  protected:
   ~I444BufferInterface() override {}
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_VIDEO_VIDEO_FRAME_BUFFER_H_