Delete IsZeroSize method.

webrtc/video_frame.h

Index: webrtc/video_frame.h
diff --git a/webrtc/video_frame.h b/webrtc/video_frame.h
index ab8e37b0ed4d41a35843ea4d9ae15632c62d588b..c3c58d7576e0642c693510e8f33acd8d4a66ec17 100644
--- a/webrtc/video_frame.h
+++ b/webrtc/video_frame.h
@@ -144,15 +144,6 @@ class VideoFrame {
   // Get render time in milliseconds.
   int64_t render_time_ms() const { return render_time_ms_; }
 
-  // Return true if and only if video_frame_buffer() is null. Which is possible
-  // only if the object was default-constructed.
-  // TODO(nisse): Deprecated. Should be deleted in the cricket::VideoFrame and
-  // webrtc::VideoFrame merge. The intention is that video_frame_buffer() never
-  // should return nullptr. To handle potentially uninitialized or non-existent
-  // frames, consider using rtc::Optional. Otherwise, IsZeroSize() can be
-  // replaced by video_frame_buffer() == nullptr.
-  bool IsZeroSize() const;
-
   // Return the underlying buffer. Never nullptr for a properly
   // initialized VideoFrame.
   // Creating a new reference breaks the HasOneRef and IsMutable