VideoFrameBuffer: Make non-const data access explicit

webrtc/common_video/video_frame.cc

Index: webrtc/common_video/video_frame.cc
diff --git a/webrtc/common_video/video_frame.cc b/webrtc/common_video/video_frame.cc
index 208a31b618f1b52f3d941c844246994d1432b106..0ebb9835d55f593be62dcf77cded48dd6402fb9c 100644
--- a/webrtc/common_video/video_frame.cc
+++ b/webrtc/common_video/video_frame.cc
@@ -152,13 +152,12 @@ void VideoFrame::Reset() {
 }
 
 uint8_t* VideoFrame::buffer(PlaneType type) {
-  return video_frame_buffer_ ? video_frame_buffer_->data(type) : nullptr;
+  return video_frame_buffer_ ? video_frame_buffer_->MutableData(type)
+                             : nullptr;
 }
 
 const uint8_t* VideoFrame::buffer(PlaneType type) const {
-  // Const cast to call the correct const-version of data.
-  const VideoFrameBuffer* const_buffer = video_frame_buffer_.get();
-  return const_buffer ? const_buffer->data(type) : nullptr;
+  return video_frame_buffer_ ? video_frame_buffer_->data(type) : nullptr;
 }
 
 int VideoFrame::allocated_size(PlaneType type) const {