Handle Alpha channel in Canvas capture

media/base/video_util.h

Index: media/base/video_util.h
diff --git a/media/base/video_util.h b/media/base/video_util.h
index e51343344a098376193636406d5652dcece7d0dc..2dec7e9371013ff3bf0442cb798cef0c90104659 100644
--- a/media/base/video_util.h
+++ b/media/base/video_util.h
@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include "base/memory/ref_counted.h"
 #include "media/base/media_export.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
@@ -92,6 +93,10 @@ MEDIA_EXPORT void CopyRGBToVideoFrame(const uint8_t* source,
                                       const gfx::Rect& region_in_frame,
                                       VideoFrame* frame);
 
+// Converts a frame with YV12A format into I420 by dropping alpha channel.
+MEDIA_EXPORT scoped_refptr<VideoFrame> WrapAsI420VideoFrame(
+    const scoped_refptr<VideoFrame>& frame);
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_UTIL_H_