Allow WebExternalTextureLayerClient to work with mailboxes.

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index b73c82832ece9195b8038d5bf5e53cb76a69a5c8..5561b0cb3a138e7184ef29eb3d538e7bb8dc7e09 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -471,7 +471,7 @@ void Layer::SetExternalTexture(Texture* texture) {
     // Switch to a different type of layer.
     if (has_texture) {
       scoped_refptr<cc::TextureLayer> new_layer =
-          cc::TextureLayer::Create(this);
+          cc::TextureLayer::Create(this, false);
       new_layer->SetFlipped(texture_->flipped());
       SwitchToLayer(new_layer);
       texture_layer_ = new_layer;