Update test code to use I420Buffer when writing pixel data.

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..ce1da3d85964982d056a1f579a90e68dad0baef6 100644
--- a/webrtc/common_video/libyuv/include/webrtc_libyuv.h
+++ b/webrtc/common_video/libyuv/include/webrtc_libyuv.h
@@ -94,6 +94,8 @@ int ExtractBuffer(const VideoFrame& input_frame, size_t size, uint8_t* buffer);
 //   - dst_frame        : Reference to a destination frame.
 // Return value: 0 if OK, < 0 otherwise.
 
+// TODO(nisse): Deprecated, see
+// https://bugs.chromium.org/p/webrtc/issues/detail?id=5921.
 int ConvertToI420(VideoType src_video_type,
                   const uint8_t* src_frame,
                   int crop_x,
@@ -120,8 +122,13 @@ 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 VideoFrameBuffer& ref_buffer,
+                const VideoFrameBuffer& test_buffer);
+
 // Compute SSIM for an I420 frame (all planes).
 double I420SSIM(const VideoFrame* ref_frame, const VideoFrame* test_frame);
+double I420SSIM(const VideoFrameBuffer& ref_buffer,
+                const VideoFrameBuffer& test_buffer);
 
 }  // namespace webrtc