cc: Compute draw transforms dynamically.

cc/trees/property_tree.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_H_
 #define CC_TREES_PROPERTY_TREE_H_
 
 #include <stddef.h>
 
+#include <map>
 #include <memory>
 #include <unordered_map>
 #include <vector>
 
 #include "cc/animation/element_id.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/synced_property.h"
 #include "cc/output/filter_operations.h"
 #include "ui/gfx/geometry/rect_f.h"
 #include "ui/gfx/geometry/scroll_offset.h"
@@ skipping 494 matching lines @@
 
   // TODO(sunxd): Move screen space transforms here if it can improve
   // performance.
   DrawTransformData()
       : update_number(-1), transforms(gfx::Transform(), gfx::Transform()) {}
 };
 
 struct PropertyTreesCachedData {
   int property_tree_update_number;
   std::vector<AnimationScaleData> animation_scales;
-  mutable std::vector<std::unordered_map<int, DrawTransformData>>
-      draw_transforms;
+  mutable std::vector<std::map<int, DrawTransformData>> draw_transforms;
 
   PropertyTreesCachedData();
   ~PropertyTreesCachedData();
 };
 
 class CC_EXPORT PropertyTrees final {
  public:
   PropertyTrees();
   PropertyTrees(const PropertyTrees& other) = delete;
   ~PropertyTrees();
@@ skipping 86 matching lines @@
   gfx::Vector2dF inner_viewport_container_bounds_delta_;
   gfx::Vector2dF outer_viewport_container_bounds_delta_;
   gfx::Vector2dF inner_viewport_scroll_bounds_delta_;
 
   PropertyTreesCachedData cached_data_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_PROPERTY_TREE_H_