Adjust for initial cropping when adapting frame.

webrtc/sdk/objc/Framework/Classes/Video/RTCCVPixelBuffer.mm

 /*
  *  Copyright 2017 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.
  */
 
 #import "WebRTC/RTCVideoFrameBuffer.h"
 
 #include "webrtc/common_video/libyuv/include/webrtc_libyuv.h"
 #include "webrtc/rtc_base/checks.h"
 #include "webrtc/rtc_base/logging.h"
 
 @implementation RTCCVPixelBuffer {
   int _width;
   int _height;
   int _bufferWidth;
   int _bufferHeight;
   int _cropWidth;
   int _cropHeight;
-  int _cropX;
-  int _cropY;
 }
 
 @synthesize pixelBuffer = _pixelBuffer;
+@synthesize cropX = _cropX;
+@synthesize cropY = _cropY;
 
 - (instancetype)initWithPixelBuffer:(CVPixelBufferRef)pixelBuffer {
   return [self initWithPixelBuffer:pixelBuffer
                       adaptedWidth:CVPixelBufferGetWidth(pixelBuffer)
                      adaptedHeight:CVPixelBufferGetHeight(pixelBuffer)
                          cropWidth:CVPixelBufferGetWidth(pixelBuffer)
                         cropHeight:CVPixelBufferGetHeight(pixelBuffer)
                              cropX:0
                              cropY:0];
 }
@@ skipping 140 matching lines @@
                                    i420Buffer.strideV,
                                    i420Buffer.width,
                                    i420Buffer.height);
 
   CVPixelBufferUnlockBaseAddress(_pixelBuffer, kCVPixelBufferLock_ReadOnly);
 
   return i420Buffer;
 }
 
 @end