Update from https://crrev.com/318214

cc/trees/property_tree_builder.h

 // Copyright 2014 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.
 
 #ifndef CC_TREES_PROPERTY_TREE_BUILDER_H_
 #define CC_TREES_PROPERTY_TREE_BUILDER_H_
 
 #include <vector>
 
 #include "cc/trees/layer_tree_host_common.h"
 #include "cc/trees/property_tree.h"
 
 namespace cc {
 
 class LayerTreeHost;
 
 class PropertyTreeBuilder {
  public:
+  // Building an opacity tree is optional, and can be skipped by passing
+  // in a null |opacity_tree|.
   static void BuildPropertyTrees(Layer* root_layer,
                                  const Layer* page_scale_layer,
                                  float page_scale_factor,
                                  float device_scale_factor,
                                  const gfx::Rect& viewport,
                                  const gfx::Transform& device_transform,
                                  TransformTree* transform_tree,
-                                 ClipTree* clip_tree);
+                                 ClipTree* clip_tree,
+                                 OpacityTree* opacity_tree);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_PROPERTY_TREE_BUILDER_H_