Delete IsZeroSize method.

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 b1721b4bc4a1963f06c3824e6b80692bb0e1e0e6..cf7bda4b46f4b2bf39318dfec95eed7f94fd778a 100644
--- a/webrtc/common_video/video_frame.cc
+++ b/webrtc/common_video/video_frame.cc
@@ -146,10 +146,6 @@ int VideoFrame::height() const {
   return video_frame_buffer_ ? video_frame_buffer_->height() : 0;
 }
 
-bool VideoFrame::IsZeroSize() const {
-  return !video_frame_buffer_;
-}
-
 const rtc::scoped_refptr<VideoFrameBuffer>& VideoFrame::video_frame_buffer()
     const {
   return video_frame_buffer_;