Delete VideoFrame default constructor, and IsZeroSize method.

webrtc/common_video/libyuv/webrtc_libyuv.cc

Index: webrtc/common_video/libyuv/webrtc_libyuv.cc
diff --git a/webrtc/common_video/libyuv/webrtc_libyuv.cc b/webrtc/common_video/libyuv/webrtc_libyuv.cc
index 6bfb1799ee12d5d6ff567ff0ea83f3301982d304..0bb592d73348c776d6eeda966af97c2847ae2603 100644
--- a/webrtc/common_video/libyuv/webrtc_libyuv.cc
+++ b/webrtc/common_video/libyuv/webrtc_libyuv.cc
@@ -128,8 +128,6 @@ int PrintVideoFrame(const VideoFrameBuffer& frame, FILE* file) {
 }
 
 int PrintVideoFrame(const VideoFrame& frame, FILE* file) {
-  if (frame.IsZeroSize())
-    return -1;
   return PrintVideoFrame(*frame.video_frame_buffer(), file);
 }