Revert of Delete VideoFrame default constructor, and IsZeroSize method.

webrtc/video_frame.h

 /*
  *  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.
  */
 
 #ifndef WEBRTC_VIDEO_FRAME_H_
 #define WEBRTC_VIDEO_FRAME_H_
 
 #include "webrtc/base/scoped_ref_ptr.h"
 #include "webrtc/base/timeutils.h"
 #include "webrtc/common_types.h"
 #include "webrtc/common_video/include/video_frame_buffer.h"
 #include "webrtc/common_video/rotation.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 
 class VideoFrame {
  public:
+  // TODO(nisse): Deprecated. Using the default constructor violates the
+  // reasonable assumption that video_frame_buffer() returns a valid buffer.
+  VideoFrame();
+
   // TODO(nisse): This constructor is consistent with
   // cricket::WebRtcVideoFrame. After the class
   // cricket::WebRtcVideoFrame and its baseclass cricket::VideoFrame
   // are deleted, we should consider whether or not we want to stick
   // to this style and deprecate the other constructors.
   VideoFrame(const rtc::scoped_refptr<VideoFrameBuffer>& buffer,
              webrtc::VideoRotation rotation,
              int64_t timestamp_us);
 
   // Preferred constructor.
@@ skipping 60 matching lines @@
   // Set render time in milliseconds.
   void set_render_time_ms(int64_t render_time_ms) {
     set_timestamp_us(render_time_ms * rtc::kNumMicrosecsPerMillisec);;
   }
 
   // Get render time in milliseconds.
   int64_t render_time_ms() const {
     return timestamp_us() / rtc::kNumMicrosecsPerMillisec;
   }
 
+  // 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.
   rtc::scoped_refptr<webrtc::VideoFrameBuffer> video_frame_buffer() const;
 
   // Return true if the frame is stored in a texture.
   bool is_texture() const {
     return video_frame_buffer() &&
            video_frame_buffer()->native_handle() != nullptr;
   }
 
@@ skipping 49 matching lines @@
   int qp_ = -1;  // Quantizer value.
 
   // When an application indicates non-zero values here, it is taken as an
   // indication that all future frames will be constrained with those limits
   // until the application indicates a change again.
   PlayoutDelay playout_delay_ = {-1, -1};
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_VIDEO_FRAME_H_