Add method on AVFoundation capturer to adapt output format.

webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.h

 /*
  *  Copyright 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 40 matching lines @@
 
   // Switches the camera being used (either front or back).
   void SetUseBackCamera(bool useBackCamera);
   bool GetUseBackCamera() const;
 
   // Converts the sample buffer into a cricket::CapturedFrame and signals the
   // frame for capture.
   void CaptureSampleBuffer(CMSampleBufferRef sample_buffer,
                            webrtc::VideoRotation rotation);
 
+  // Called to adjust the size of output frames to supplied |width| and
+  // |height|. Also drops frames to make the output match |fps|.
+  void AdaptOutputFormat(int width, int height, int fps);
+
  private:
   RTCAVFoundationVideoCapturerInternal *_capturer;
   webrtc::I420BufferPool _buffer_pool;
 };  // AVFoundationVideoCapturer
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_OBJC_AVFOUNDATION_VIDEO_CAPTURER_H_