Handle Alpha channel in Canvas capture

chrome/renderer/media/cast_rtp_stream.cc

 // Copyright 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 "chrome/renderer/media/cast_rtp_stream.h"
 
 #include <stdint.h>
 #include <algorithm>
 #include <utility>
 
@@ skipping 311 matching lines @@
       // These parameters are already bound when callback is created.
       const CastRtpStream::ErrorCallback& error_callback,
       const scoped_refptr<media::cast::VideoFrameInput> frame_input,
       // These parameters are passed for each frame.
       const scoped_refptr<media::VideoFrame>& frame,
       base::TimeTicks estimated_capture_time) {
     const base::TimeTicks timestamp = estimated_capture_time.is_null()
                                           ? base::TimeTicks::Now()
                                           : estimated_capture_time;
 
+    if (!(frame->IsMappable() &&
+          (frame->format() == media::PIXEL_FORMAT_I420 ||
+           frame->format() == media::PIXEL_FORMAT_YV12 ||
+           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();
+
     // Used by chrome/browser/extension/api/cast_streaming/performance_test.cc
     TRACE_EVENT_INSTANT2(
         "cast_perf_test", "MediaStreamVideoSink::OnVideoFrame",
         TRACE_EVENT_SCOPE_THREAD,
         "timestamp",  timestamp.ToInternalValue(),
         "time_delta", frame->timestamp().ToInternalValue());
     frame_input->InsertRawVideoFrame(frame, timestamp);
   }
 
   // Attach this sink to a video track represented by |track_|.
@@ skipping 285 matching lines @@
   DCHECK(content::RenderThread::Get());
   DVLOG(1) << "CastRtpStream::DidEncounterError(" << message << ") = "
            << (IsAudio() ? "audio" : "video");
   // Save the WeakPtr first because the error callback might delete this object.
   base::WeakPtr<CastRtpStream> ptr = weak_factory_.GetWeakPtr();
   error_callback_.Run(message);
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
       base::Bind(&CastRtpStream::Stop, ptr));
 }