media: Add support for playback of VP8 Alpha video streams

cc/layers/video_layer_impl.cc

Index: cc/layers/video_layer_impl.cc
diff --git a/cc/layers/video_layer_impl.cc b/cc/layers/video_layer_impl.cc
index 94125d6735cd18c7ecd53cbd50c42929fbb45736..2449c08cdb375603101bbec6ad4a25b5be055aea 100644
--- a/cc/layers/video_layer_impl.cc
+++ b/cc/layers/video_layer_impl.cc
@@ -133,6 +133,7 @@ void VideoLayerImpl::WillDrawInternal(ResourceProvider* resource_provider) {
   convert_yuv_ =
       resource_provider->default_resource_type() == ResourceProvider::Bitmap &&
       (format_ == media::VideoFrame::YV12 ||
+       format_ == media::VideoFrame::YV12A ||
        format_ == media::VideoFrame::YV16);
 
   if (convert_yuv_)
@@ -216,6 +217,25 @@ void VideoLayerImpl::AppendQuads(QuadSink* quad_sink,
       quad_sink->Append(yuv_video_quad.PassAs<DrawQuad>(), append_quads_data);
       break;
     }
+    case media::VideoFrame::YV12A: {
+      // YUV software decoder.
+      const FramePlane& y_plane = frame_planes_[media::VideoFrame::kYPlane];
+      const FramePlane& u_plane = frame_planes_[media::VideoFrame::kUPlane];
+      const FramePlane& v_plane = frame_planes_[media::VideoFrame::kVPlane];
+      const FramePlane& a_plane = frame_planes_[media::VideoFrame::kAPlane];
+      gfx::SizeF tex_scale(tex_width_scale, tex_height_scale);
+      scoped_ptr<YUVVideoDrawQuad> yuva_video_quad = YUVVideoDrawQuad::Create();
+      yuva_video_quad->SetNew(shared_quad_state,
+                              quad_rect,
+                              opaque_rect,
+                              tex_scale,
+                              y_plane,
+                              u_plane,
+                              v_plane,
+                              a_plane);
+      quad_sink->Append(yuva_video_quad.PassAs<DrawQuad>(), append_quads_data);
+      break;
+    }
     case media::VideoFrame::RGB32: {
       // RGBA software decoder: a converted YUV frame (see: convert_yuv_).
       const FramePlane& plane = frame_planes_[media::VideoFrame::kRGBPlane];
@@ -332,7 +352,9 @@ static gfx::Size VideoFrameDimension(media::VideoFrame* frame, int plane) {
   gfx::Size dimensions = frame->coded_size();
   switch (frame->format()) {
     case media::VideoFrame::YV12:
-      if (plane != media::VideoFrame::kYPlane) {
+    case media::VideoFrame::YV12A:
+      if (plane != media::VideoFrame::kYPlane &&
+          plane != media::VideoFrame::kAPlane) {
         dimensions.set_width(dimensions.width() / 2);
         dimensions.set_height(dimensions.height() / 2);
       }
@@ -370,6 +392,7 @@ static GLenum ConvertVFCFormatToGLenum(const media::VideoFrame::Format format) {
   switch (format) {
     case media::VideoFrame::YV12:
     case media::VideoFrame::YV16:
+    case media::VideoFrame::YV12A:
       return GL_LUMINANCE;
     case media::VideoFrame::RGB32:
       return GL_RGBA;