New method CreateScaledFrame in the VideoFrameFactory interface.

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 6f082dee9bae928fbb005027b7262f03bdde3053..6152bc7a62361ac45f0116f23aa05429109d72fd 100644
--- a/webrtc/common_video/include/video_frame_buffer.h
+++ b/webrtc/common_video/include/video_frame_buffer.h
@@ -122,6 +122,20 @@ class I420Buffer : public VideoFrameBuffer {
   static rtc::scoped_refptr<I420Buffer> Copy(
       const rtc::scoped_refptr<VideoFrameBuffer>& buffer);
 
+  static rtc::scoped_refptr<I420Buffer> Scale(
+      const rtc::scoped_refptr<VideoFrameBuffer>& buffer,
+      int dst_width,
+      int dst_height);
+
+  static rtc::scoped_refptr<I420Buffer> CropAndScale(
+      const rtc::scoped_refptr<VideoFrameBuffer>& buffer,
+      int crop_x,
+      int crop_y,
+      int crop_width,
+      int crop_height,
+      int dst_width,
+      int dst_height);
+
  protected:
   ~I420Buffer() override;
 
@@ -187,6 +201,15 @@ class WrappedI420Buffer : public webrtc::VideoFrameBuffer {
 
   rtc::scoped_refptr<VideoFrameBuffer> NativeToI420Buffer() override;
 
+  // Helper function to crop |buffer| without making a deep copy. May
+  // only be used for non-native frames.
+  static rtc::scoped_refptr<WrappedI420Buffer> ShallowCrop(
+    const rtc::scoped_refptr<VideoFrameBuffer>& buffer,
+    int crop_x,
+    int crop_y,
+    int cropped_width,
+    int cropped_height);
+
  private:
   friend class rtc::RefCountedObject<WrappedI420Buffer>;
   ~WrappedI420Buffer() override;