Move direct use of VideoCapturer::VideoAdapter to VideoSinkWants.

webrtc/media/base/videosourceinterface.h

 /*
  *  Copyright (c) 2016 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_MEDIA_BASE_VIDEOSOURCEINTERFACE_H_
 #define WEBRTC_MEDIA_BASE_VIDEOSOURCEINTERFACE_H_
 
+#include <limits>
+
 #include "webrtc/media/base/videosinkinterface.h"
 #include "webrtc/base/callback.h"
+#include "webrtc/base/optional.h"
 
 namespace rtc {
 
 // VideoSinkWants is used for notifying the source of properties a video frame
 // should have when it is delivered to a certain sink.
 struct VideoSinkWants {
   bool operator==(const VideoSinkWants& rh) const {
     return rotation_applied == rh.rotation_applied;
   }
   bool operator!=(const VideoSinkWants& rh) const { return !operator==(rh); }
 
   // Tells the source whether the sink wants frames with rotation applied.
   // By default, the rotation is applied by the source.
   bool rotation_applied = true;
+
+  // Tells the source the maximum number of pixels the sink wants.
+  rtc::Optional<int> max_number_of_pixels;
 };
 
 template <typename VideoFrameT>
 class VideoSourceInterface {
  public:
   virtual void AddOrUpdateSink(VideoSinkInterface<VideoFrameT>* sink,
                                const VideoSinkWants& wants) = 0;
   // RemoveSink must guarantee that at the time the method returns,
   // there is no current and no future calls to VideoSinkInterface::OnFrame.
   virtual void RemoveSink(VideoSinkInterface<VideoFrameT>* sink) = 0;
 
  protected:
   virtual ~VideoSourceInterface() {}
 };
 
 }  // namespace rtc
 #endif  // WEBRTC_MEDIA_BASE_VIDEOSOURCEINTERFACE_H_