Handle Alpha channel in Canvas capture

content/renderer/pepper/pepper_video_source_host.cc

 // Copyright (c) 2013 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_video_source_host.h"
 
 #include <string.h>
 
 #include "base/bind.h"
 #include "base/numerics/safe_conversions.h"
@@ skipping 41 matching lines @@
     const base::WeakPtr<PepperVideoSourceHost>& host)
     : host_(host) {}
 
 PepperVideoSourceHost::FrameReceiver::~FrameReceiver() {}
 
 void PepperVideoSourceHost::FrameReceiver::GotFrame(
     const scoped_refptr<media::VideoFrame>& frame) {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!host_)
     return;
+
+  if (!(frame->IsMappable() &&
+        (frame->format() == media::PIXEL_FORMAT_I420 ||
+         frame->format() == media::PIXEL_FORMAT_YV12A))) {
+    NOTREACHED();
+    return;
+  }
+
+  // Drop alpha channel since we do not support it yet.
+  if (frame->format() == media::PIXEL_FORMAT_YV12A)
+    frame->DropYV12AAlphaChannel();
+
   // Hold a reference to the new frame and release the previous.
   host_->last_frame_ = frame;
   if (host_->get_frame_pending_)
     host_->SendGetFrameReply();
 }
 
 PepperVideoSourceHost::PepperVideoSourceHost(RendererPpapiHost* host,
                                              PP_Instance instance,
                                              PP_Resource resource)
     : ResourceHost(host->GetPpapiHost(), instance, resource),
@@ skipping 230 matching lines @@
   if (frame_source_.get() && !stream_url_.empty())
     frame_source_->Close(frame_receiver_.get());
 
   frame_source_.reset(NULL);
   stream_url_.clear();
 
   shared_image_ = NULL;
 }
 
 }  // namespace content