Revert of Delete VideoFrame default constructor, and IsZeroSize method.

webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc

 /*
  *  Copyright (c) 2014 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 468 matching lines @@
   const uint32_t min_intra_size = 300;
   return (target_pct < min_intra_size) ? min_intra_size : target_pct;
 }
 
 int VP9EncoderImpl::Encode(const VideoFrame& input_image,
                            const CodecSpecificInfo* codec_specific_info,
                            const std::vector<FrameType>* frame_types) {
   if (!inited_) {
     return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
   }
+  if (input_image.IsZeroSize()) {
+    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
+  }
   if (encoded_complete_callback_ == NULL) {
     return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
   }
   FrameType frame_type = kVideoFrameDelta;
   // We only support one stream at the moment.
   if (frame_types && frame_types->size() > 0) {
     frame_type = (*frame_types)[0];
   }
   RTC_DCHECK_EQ(input_image.width(), raw_->d_w);
   RTC_DCHECK_EQ(input_image.height(), raw_->d_h);
@@ skipping 497 matching lines @@
   frame_buffer_pool_.ClearPool();
   inited_ = false;
   return WEBRTC_VIDEO_CODEC_OK;
 }
 
 const char* VP9DecoderImpl::ImplementationName() const {
   return "libvpx";
 }
 
 }  // namespace webrtc