cc: Add flag to disable future mask tiling.

cc/layers/layer.cc

 // Copyright 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/layer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 401 matching lines @@
     inputs_.mask_layer->RemoveFromParent();
   }
   inputs_.mask_layer = mask_layer;
   if (inputs_.mask_layer.get()) {
     // The mask layer should not have any children.
     DCHECK(inputs_.mask_layer->children().empty());
 
     inputs_.mask_layer->RemoveFromParent();
     DCHECK(!inputs_.mask_layer->parent());
     inputs_.mask_layer->SetParent(this);
-    if (inputs_.filters.IsEmpty()) {
+    if (inputs_.filters.IsEmpty() &&
+        (!layer_tree_host_ ||
+         layer_tree_host_->GetSettings().enable_mask_tiling)) {
       inputs_.mask_layer->SetLayerMaskType(
           Layer::LayerMaskType::MULTI_TEXTURE_MASK);
     } else {
       inputs_.mask_layer->SetLayerMaskType(
           Layer::LayerMaskType::SINGLE_TEXTURE_MASK);
     }
   }
   SetSubtreePropertyChanged();
   SetNeedsFullTreeSync();
 }
@@ skipping 1146 matching lines @@
       ->num_copy_requests_in_subtree;
 }
 
 gfx::Transform Layer::screen_space_transform() const {
   DCHECK_NE(transform_tree_index_, TransformTree::kInvalidNodeId);
   return draw_property_utils::ScreenSpaceTransform(
       this, layer_tree_host_->property_trees()->transform_tree);
 }
 
 }  // namespace cc