Handle Alpha channel in Canvas capture

content/renderer/media/video_track_adapter.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/media/video_track_adapter.h"
 
 #include <algorithm>
 #include <limits>
 #include <utility>
 
@@ skipping 248 matching lines @@
 
     const gfx::Size desired_size(desired_width, desired_height);
 
     // Get the largest centered rectangle with the same aspect ratio of
     // |desired_size| that fits entirely inside of |frame->visible_rect()|.
     // This will be the rect we need to crop the original frame to.
     // From this rect, the original frame can be scaled down to |desired_size|.
     const gfx::Rect region_in_frame =
         media::ComputeLetterboxRegion(frame->visible_rect(), desired_size);
 
-    video_frame =
-        media::VideoFrame::WrapVideoFrame(frame, region_in_frame, desired_size);
+    video_frame = media::VideoFrame::WrapVideoFrame(
+        frame, frame->format(), region_in_frame, desired_size);
     if (!video_frame)
       return;
     video_frame->AddDestructionObserver(
         base::Bind(&ReleaseOriginalFrame, frame));
 
     DVLOG(3) << "desired size  " << desired_size.ToString()
              << " output natural size "
              << video_frame->natural_size().ToString()
              << " output visible rect  "
              << video_frame->visible_rect().ToString();
@@ skipping 233 matching lines @@
   }
 
   io_task_runner_->PostDelayedTask(
       FROM_HERE, base::Bind(&VideoTrackAdapter::CheckFramesReceivedOnIO, this,
                             set_muted_state_callback, frame_counter_),
       base::TimeDelta::FromSecondsD(kNormalFrameTimeoutInFrameIntervals /
                                     source_frame_rate_));
 }
 
 }  // namespace content