Revert of Delete unused and almost unused frame-related methods.

webrtc/video_frame.h

Index: webrtc/video_frame.h
diff --git a/webrtc/video_frame.h b/webrtc/video_frame.h
index 0f2b9a68afd1a15691ffefccee2377d8902cddb9..b9ba69bb05283d031c63bcadf89d66fd47a805e2 100644
--- a/webrtc/video_frame.h
+++ b/webrtc/video_frame.h
@@ -121,6 +121,14 @@
   const rtc::scoped_refptr<webrtc::VideoFrameBuffer>& video_frame_buffer()
       const;
 
+  // Set the underlying buffer.
+  void set_video_frame_buffer(
+      const rtc::scoped_refptr<webrtc::VideoFrameBuffer>& buffer);
+
+  // Convert native-handle frame to memory-backed I420 frame. Should not be
+  // called on a non-native-handle frame.
+  VideoFrame ConvertNativeToI420Frame() const;
+
   // Return true if the frame is stored in a texture.
   bool is_texture() {
     return video_frame_buffer() &&