Adding VP8 Alpha support in Media Source

media/webm/webm_video_client.cc

Index: media/webm/webm_video_client.cc
diff --git a/media/webm/webm_video_client.cc b/media/webm/webm_video_client.cc
index b4e729e36eeab290126cd7bb80b694bc6340ecab..1d0cbcb2ac40d36baf4c55abf4cf3e05e877c411 100644
--- a/media/webm/webm_video_client.cc
+++ b/media/webm/webm_video_client.cc
@@ -27,6 +27,7 @@ void WebMVideoClient::Reset() {
   display_width_ = -1;
   display_height_ = -1;
   display_unit_ = -1;
+  alpha_mode_ = -1;
 }
 
 bool WebMVideoClient::InitializeConfig(
@@ -47,6 +48,9 @@ bool WebMVideoClient::InitializeConfig(
     return false;
   }
 
+  VideoFrame::Format format =
+      (alpha_mode_ == 1) ? VideoFrame::YV12A : VideoFrame::YV12;
+
   if (pixel_width_ <= 0 || pixel_height_ <= 0)
     return false;
 
@@ -93,9 +97,8 @@ bool WebMVideoClient::InitializeConfig(
   }
 
   config->Initialize(
-      video_codec, profile, VideoFrame::YV12, coded_size,
-      visible_rect, natural_size, extra_data, extra_data_size,
-      is_encrypted, true);
+      video_codec, profile, format, coded_size, visible_rect, natural_size,
+      extra_data, extra_data_size, is_encrypted, true);
   return config->IsValidConfig();
 }
 
@@ -130,6 +133,9 @@ bool WebMVideoClient::OnUInt(int id, int64 val) {
     case kWebMIdDisplayUnit:
       dst = &display_unit_;
       break;
+    case kWebMIdAlphaMode:
+      dst = &alpha_mode_;
+      break;
     default:
       return true;
   }