Refactor scaling.

webrtc/common_video/include/video_frame_buffer.h

Index: webrtc/common_video/include/video_frame_buffer.h
diff --git a/webrtc/common_video/include/video_frame_buffer.h b/webrtc/common_video/include/video_frame_buffer.h
index 984bd50d674e78d7e7aedfc252fcfef8810b6963..55303ca608c70034c52f493af7c5f6baa87c79b1 100644
--- a/webrtc/common_video/include/video_frame_buffer.h
+++ b/webrtc/common_video/include/video_frame_buffer.h
@@ -109,6 +109,23 @@ class I420Buffer : public VideoFrameBuffer {
   static rtc::scoped_refptr<I420Buffer> Copy(
       const rtc::scoped_refptr<VideoFrameBuffer>& buffer);
 
+  // Only the most generally useful operations should be methods on
+  // this class, for more specialized operations, use
+  // MutableDataY(,U,V) to get write access.
+
+  // Crop the input buffer, then scale it to the size of this buffer.
+  void CropAndScale(const rtc::scoped_refptr<VideoFrameBuffer>& buffer,
+                    int offset_x,
+                    int offset_y,
+                    int crop_width,
+                    int crop_height);
+
+  // The common case of a center crop, when needed to maintain the
+  // same aspect ratio.
+  static void CenterCropAndScale(
+      const rtc::scoped_refptr<I420Buffer>& dst,
+      const rtc::scoped_refptr<VideoFrameBuffer>& src);
+
  protected:
   ~I420Buffer() override;