Move MutableDataY{,U,V} methods to I420Buffer only.

webrtc/common_video/libyuv/include/webrtc_libyuv.h

Index: webrtc/common_video/libyuv/include/webrtc_libyuv.h
diff --git a/webrtc/common_video/libyuv/include/webrtc_libyuv.h b/webrtc/common_video/libyuv/include/webrtc_libyuv.h
index ec3720e442bc9621fb9e7cdb6696c964073051f7..00661fb1b2192f04e7a835b4cdd26a844b0249d2 100644
--- a/webrtc/common_video/libyuv/include/webrtc_libyuv.h
+++ b/webrtc/common_video/libyuv/include/webrtc_libyuv.h
@@ -102,7 +102,7 @@ int ConvertToI420(VideoType src_video_type,
                   int src_height,
                   size_t sample_size,
                   VideoRotation rotation,
-                  VideoFrame* dst_frame);
+                  const rtc::scoped_refptr<I420Buffer>& dst_buffer);

[magjed_webrtc, 2016/08/25 11:12:56]

If dst_buffer is an output argument, you need to use a pointer to a
scoped_refptr. (Or a pointer to an I420Buffer if we will allow that).

[nisse-webrtc, 2016/08/25 11:31:35]

I think the const is ok here; the scoped_refptr itself is not modified in any
way, but the object it points to have it's pixel buffers overwritten.

[magjed_webrtc, 2016/08/25 11:49:08]

Yes, using const here will compile, but according to the style guide you need to
use a pointer to a scoped_refptr if it's an output.

[nisse-webrtc, 2016/08/25 12:38:40]

I'll do that then. That makes sense in some way. But it gets awkward to
dereference, like

  int dst_width = (*dst_buffer)->width();

I think I'll count that as one point for using a raw pointer argument instead.

 
 // Convert From I420
 // Input:
@@ -120,8 +120,12 @@ int ConvertFromI420(const VideoFrame& src_frame,
 // Compute PSNR for an I420 frame (all planes).
 // Returns the PSNR in decibel, to a maximum of kInfinitePSNR.
 double I420PSNR(const VideoFrame* ref_frame, const VideoFrame* test_frame);
+double I420PSNR(const rtc::scoped_refptr<VideoFrameBuffer>& ref_buffer,
+                const rtc::scoped_refptr<VideoFrameBuffer>& test_buffer);
 // Compute SSIM for an I420 frame (all planes).
 double I420SSIM(const VideoFrame* ref_frame, const VideoFrame* test_frame);
+double I420SSIM(const rtc::scoped_refptr<VideoFrameBuffer>& ref_buffer,
+                const rtc::scoped_refptr<VideoFrameBuffer>& test_buffer);
 
 }  // namespace webrtc