cc: Distinguish single texture mask from normal masks

cc/layers/picture_image_layer.cc

Index: cc/layers/picture_image_layer.cc
diff --git a/cc/layers/picture_image_layer.cc b/cc/layers/picture_image_layer.cc
index 67049c37bbf2f7c458f3c87854ebbc84e82e0a9f..0e909d6b8a61e12dcf6836727e292e0a6b7b1e85 100644
--- a/cc/layers/picture_image_layer.cc
+++ b/cc/layers/picture_image_layer.cc
@@ -27,7 +27,7 @@ PictureImageLayer::~PictureImageLayer() {
 
 std::unique_ptr<LayerImpl> PictureImageLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
-  auto layer_impl = PictureLayerImpl::Create(tree_impl, id(), is_mask());
+  auto layer_impl = PictureLayerImpl::Create(tree_impl, id(), mask_type());
   layer_impl->set_is_directly_composited_image(true);
   return std::move(layer_impl);
 }