Handle Alpha channel in Canvas capture

content/renderer/pepper/pepper_video_source_host.cc

Index: content/renderer/pepper/pepper_video_source_host.cc
diff --git a/content/renderer/pepper/pepper_video_source_host.cc b/content/renderer/pepper/pepper_video_source_host.cc
index db20126b141a6f30c413748970c36a7bb5f36e5d..cac83ebf76ec26aeaeda2896cc00edec8dbe7ada 100644
--- a/content/renderer/pepper/pepper_video_source_host.cc
+++ b/content/renderer/pepper/pepper_video_source_host.cc
@@ -12,6 +12,7 @@
 #include "content/renderer/media/video_track_to_pepper_adapter.h"
 #include "content/renderer/pepper/ppb_image_data_impl.h"
 #include "content/renderer/render_thread_impl.h"
+#include "media/base/video_util.h"
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/host/dispatch_host_message.h"
 #include "ppapi/host/ppapi_host.h"
@@ -55,10 +56,21 @@ PepperVideoSourceHost::FrameReceiver::FrameReceiver(
 PepperVideoSourceHost::FrameReceiver::~FrameReceiver() {}
 
 void PepperVideoSourceHost::FrameReceiver::GotFrame(
-    const scoped_refptr<media::VideoFrame>& frame) {
+    const scoped_refptr<media::VideoFrame>& video_frame) {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!host_)
     return;
+
+  if (!(video_frame->format() == media::PIXEL_FORMAT_I420 ||
+        video_frame->format() == media::PIXEL_FORMAT_YV12A)) {

[bbudge, 2016/03/08 13:17:33]

Why is this checked here, but not in
content/renderer/pepper/pepper_media_stream_video_track_host.cc?

[emircan, 2016/03/08 19:01:46]

With this patch, each sink is expected to handle a new format. While doing that,
I wanted to also make it very clear which formats are expected as input so I
included these checks. 

In PepperMediaStreamVideoTrackHost::OnVideoFrame, ToPpapiFormat method checks
the format[0] and handles unexpected formats. I didn't want to change that
logic. Still, if you think I should remove the checks here or add it there, I
can do that. WDYT?

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

[bbudge, 2016/03/08 20:13:34]

OK, this is fine then.

+    NOTREACHED();
+    return;
+  }
+  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);
+
   // Hold a reference to the new frame and release the previous.
   host_->last_frame_ = frame;
   if (host_->get_frame_pending_)