Handle Alpha channel in Canvas capture

content/renderer/media/video_track_recorder.cc

 // Copyright 2015 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_recorder.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 174 matching lines @@
                             this, frame, capture_timestamp));
 }
 
 void VideoTrackRecorder::VpxEncoder::EncodeOnEncodingThread(
     const scoped_refptr<VideoFrame>& frame,
     base::TimeTicks capture_timestamp) {
   TRACE_EVENT0("video",
                "VideoTrackRecorder::VpxEncoder::EncodeOnEncodingThread");
   DCHECK(encoding_thread_->task_runner()->BelongsToCurrentThread());
 
+  if (!(frame->IsMappable() &&

[mcasas, 2016/02/25 22:06:25]

Why add this here now? (Same elsewhere).

[emircan, 2016/02/26 01:33:08]

Removing IsMappable() checks.

+        (frame->format() == media::PIXEL_FORMAT_I420 ||
+         frame->format() == media::PIXEL_FORMAT_YV12A))) {
+    NOTREACHED();
+    return;
+  }

[mcasas, 2016/02/25 22:06:25]

Judgment call: turn this into a DCHECK() and
let it continue? AFAIK there's nothing but I420
frames on the renderer MSs before this CL.

[emircan, 2016/02/26 01:33:08]

I actually started with DCHECKs but then found [0], so I decided to follow the
pattern. I know that DCHECKs would be better for performance, but there might be
cases out in the wild that isn't covered by the current tests. It is a hard
judgment call. WDYT?

[0]
https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/m...

+
+  // Drop alpha channel since we do not support it yet.
+  if (frame->format() == media::PIXEL_FORMAT_YV12A)
+    frame->DropYV12AAlphaChannel();
+
   const gfx::Size frame_size = frame->visible_rect().size();
   if (!IsInitialized() ||
       gfx::Size(codec_config_.g_w, codec_config_.g_h) != frame_size) {
     ConfigureEncoding(frame_size);
   }
 
   vpx_image_t vpx_image;
   vpx_image_t* const result = vpx_img_wrap(&vpx_image,
                                            VPX_IMG_FMT_I420,
                                            frame_size.width(),
@@ skipping 189 matching lines @@
   encoder_->set_paused(false);
 }
 
 void VideoTrackRecorder::OnVideoFrameForTesting(
     const scoped_refptr<media::VideoFrame>& frame,
     base::TimeTicks timestamp) {
   encoder_->StartFrameEncode(frame, timestamp);
 }
 
 }  // namespace content