Pass information about overlay support in a mailbox from blink to CC.

webkit/renderer/compositor_bindings/web_external_texture_layer_impl.cc

Index: webkit/renderer/compositor_bindings/web_external_texture_layer_impl.cc
diff --git a/webkit/renderer/compositor_bindings/web_external_texture_layer_impl.cc b/webkit/renderer/compositor_bindings/web_external_texture_layer_impl.cc
index 1ddf54175695cf6aebac14ec2c9bbebc86590a91..320aa2297f2fa7efe653bfcf80ad8978fd9597d0 100644
--- a/webkit/renderer/compositor_bindings/web_external_texture_layer_impl.cc
+++ b/webkit/renderer/compositor_bindings/web_external_texture_layer_impl.cc
@@ -82,6 +82,7 @@ bool WebExternalTextureLayerImpl::PrepareTextureMailbox(
     *mailbox =
         cc::TextureMailbox(name, GL_TEXTURE_2D, client_mailbox.syncPoint);
   }
+  mailbox->set_allow_overlay(client_mailbox.allowOverlay);
 
   if (mailbox->IsValid()) {
     *release_callback = cc::SingleReleaseCallback::Create(base::Bind(