Generalize scroll parent work in CalculateDrawProperties

cc/trees/layer_tree_host.h

 // Copyright 2011 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_LAYER_TREE_HOST_H_
 #define CC_TREES_LAYER_TREE_HOST_H_
 
 #include <limits>
 #include <list>
 #include <set>
@@ skipping 438 matching lines @@
   scoped_refptr<Layer> outer_viewport_scroll_layer_;
 
   LayerSelectionBound selection_start_;
   LayerSelectionBound selection_end_;
 
   SharedBitmapManager* shared_bitmap_manager_;
 
   ScopedPtrVector<SwapPromise> swap_promise_list_;
   std::set<SwapPromiseMonitor*> swap_promise_monitor_;
 
+  // We associate work done in CalculateDrawProperties with a sequence number
+  // to avoid having to do extra walks to clear values.
+  size_t render_surface_layer_list_id_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_