Delete VideoFrame default constructor, and IsZeroSize method.

webrtc/media/engine/fakewebrtccall.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 147 matching lines @@
   rtc::VideoSinkWants sink_wants_;
 
   bool codec_settings_set_;
   union VpxSettings {
     webrtc::VideoCodecVP8 vp8;
     webrtc::VideoCodecVP9 vp9;
   } vpx_settings_;
   bool resolution_scaling_enabled_;
   rtc::VideoSourceInterface<webrtc::VideoFrame>* source_;
   int num_swapped_frames_;
-  webrtc::VideoFrame last_frame_;
+  rtc::Optional<webrtc::VideoFrame> last_frame_;
   webrtc::VideoSendStream::Stats stats_;
   int num_encoder_reconfigurations_ = 0;
 };
 
 class FakeVideoReceiveStream final : public webrtc::VideoReceiveStream {
  public:
   explicit FakeVideoReceiveStream(webrtc::VideoReceiveStream::Config config);
 
   const webrtc::VideoReceiveStream::Config& GetConfig();
 
@@ skipping 123 matching lines @@
 
   int num_created_send_streams_;
   int num_created_receive_streams_;
 
   int audio_transport_overhead_;
   int video_transport_overhead_;
 };
 
 }  // namespace cricket
 #endif  // WEBRTC_MEDIA_ENGINE_FAKEWEBRTCCALL_H_