Change pre_encode_callback to get a const frame.

webrtc/video_send_stream.h

 /*
  *  Copyright (c) 2013 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_SEND_STREAM_H_
 #define WEBRTC_VIDEO_SEND_STREAM_H_
 
 #include <map>
 #include <string>
 
 #include "webrtc/common_types.h"
 #include "webrtc/config.h"
 #include "webrtc/frame_callback.h"
+#include "webrtc/media/base/videosinkinterface.h"
 #include "webrtc/stream.h"
 #include "webrtc/transport.h"
 #include "webrtc/media/base/videosinkinterface.h"
 
 namespace webrtc {
 
 class LoadObserver;
 class VideoEncoder;
 
 // Class to deliver captured frame to the video send stream.
@@ skipping 102 matching lines @@
 
     // Transport for outgoing packets.
     Transport* send_transport = nullptr;
 
     // Callback for overuse and normal usage based on the jitter of incoming
     // captured frames. 'nullptr' disables the callback.
     LoadObserver* overuse_callback = nullptr;
 
     // Called for each I420 frame before encoding the frame. Can be used for
     // effects, snapshots etc. 'nullptr' disables the callback.
-    I420FrameCallback* pre_encode_callback = nullptr;
+    rtc::VideoSinkInterface<VideoFrame>* pre_encode_callback = nullptr;
 
     // Called for each encoded frame, e.g. used for file storage. 'nullptr'
     // disables the callback. Also measures timing and passes the time
     // spent on encoding. This timing will not fire if encoding takes longer
     // than the measuring window, since the sample data will have been dropped.
     EncodedFrameObserver* post_encode_callback = nullptr;
 
     // Renderer for local preview. The local renderer will be called even if
     // sending hasn't started. 'nullptr' disables local rendering.
     rtc::VideoSinkInterface<VideoFrame>* local_renderer = nullptr;
@@ skipping 21 matching lines @@
   // in the config. Encoder settings are passed on to the encoder instance along
   // with the VideoStream settings.
   virtual void ReconfigureVideoEncoder(const VideoEncoderConfig& config) = 0;
 
   virtual Stats GetStats() = 0;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_VIDEO_SEND_STREAM_H_