Handle Alpha channel in Canvas capture

content/renderer/pepper/pepper_media_stream_video_track_host.cc

 // Copyright 2014 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.
 
 #include "content/renderer/pepper/pepper_media_stream_video_track_host.h"
 
 #include <stddef.h>
 
 #include "base/base64.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/rand_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "content/renderer/media/media_stream_video_track.h"
 #include "media/base/bind_to_current_loop.h"
+#include "media/base/video_util.h"
 #include "media/base/yuv_convert.h"
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/c/ppb_media_stream_video_track.h"
 #include "ppapi/c/ppb_video_frame.h"
 #include "ppapi/host/dispatch_host_message.h"
 #include "ppapi/host/host_message_context.h"
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/shared_impl/media_stream_buffer.h"
 #include "third_party/libyuv/include/libyuv.h"
 
@@ skipping 337 matching lines @@
 
     frame_deliverer_->DeliverVideoFrame(frame);
   }
 
   // Makes the frame available again for plugin.
   SendEnqueueBufferMessageToPlugin(index);
   return PP_OK;
 }
 
 void PepperMediaStreamVideoTrackHost::OnVideoFrame(
-    const scoped_refptr<VideoFrame>& frame,
+    const scoped_refptr<VideoFrame>& video_frame,
     base::TimeTicks estimated_capture_time) {
-  DCHECK(frame.get());
+  DCHECK(video_frame.get());
   // TODO(penghuang): Check |frame->end_of_stream()| and close the track.
-  PP_VideoFrame_Format ppformat = ToPpapiFormat(frame->format());
+  PP_VideoFrame_Format ppformat = ToPpapiFormat(video_frame->format());
+  scoped_refptr<media::VideoFrame> frame = video_frame;
+  // Drop alpha channel since we do not support it yet.
+  if (frame->format() == media::PIXEL_FORMAT_YV12A)
+    frame = media::WrapAsI420VideoFrame(video_frame);
+
   if (ppformat == PP_VIDEOFRAME_FORMAT_UNKNOWN)
     return;
 
   if (source_frame_size_.IsEmpty()) {
     source_frame_size_ = frame->visible_rect().size();
     source_frame_format_ = ppformat;
     InitBuffers();
   }
 
   int32_t index = buffer_manager()->DequeueBuffer();
@@ skipping 139 matching lines @@
 }
 
 void PepperMediaStreamVideoTrackHost::OnTrackStarted(
     MediaStreamSource* source,
     MediaStreamRequestResult result,
     const blink::WebString& result_name) {
   DVLOG(3) << "OnTrackStarted result: " << result;
 }
 
 }  // namespace content