Handle Alpha channel in Canvas capture

media/base/video_util.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BASE_VIDEO_UTIL_H_
 #define MEDIA_BASE_VIDEO_UTIL_H_
 
 #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"
 
 namespace media {
 
 class VideoFrame;
 
 // Computes the size of |visible_size| for a given aspect ratio.
 MEDIA_EXPORT gfx::Size GetNaturalSize(const gfx::Size& visible_size,
@@ skipping 65 matching lines @@
 MEDIA_EXPORT gfx::Size PadToMatchAspectRatio(const gfx::Size& size,
                                              const gfx::Size& target);
 
 // Copy an RGB bitmap into the specified |region_in_frame| of a YUV video frame.
 // Fills the regions outside |region_in_frame| with black.
 MEDIA_EXPORT void CopyRGBToVideoFrame(const uint8_t* source,
                                       int stride,
                                       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> DropYV12AAlphaChannel(

[mcasas, 2016/02/29 23:48:01]

I was surprised that it returned a scoped_refptr<VideoFrame>
when the name seems to imply that it drops the A channel of
the passed frame. Please update name and comment to 
reflect that it wraps a given frame into a non-alpha frame.
Hmmm what about AsOpaque() ... ?

[emircan, 2016/03/01 20:07:55]

I see your point. WrapAsOpaque() might also imply RGBA->RGB. I will go with
WrapAsI420VideoFrame(). WDYT?

+    const scoped_refptr<VideoFrame>& frame);
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_UTIL_H_