Force use of and cache render surface.

cc/trees/damage_tracker.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_DAMAGE_TRACKER_H_
 #define CC_TREES_DAMAGE_TRACKER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 18 matching lines @@
 // the screen to save GPU computation and bandwidth.
 class CC_EXPORT DamageTracker {
  public:
   static std::unique_ptr<DamageTracker> Create();
   ~DamageTracker();
 
   static void UpdateDamageTracking(
       LayerTreeImpl* layer_tree_impl,
       const RenderSurfaceList& render_surface_list);
 
-  void DidDrawDamagedArea() { current_damage_ = DamageAccumulator(); }
+  void DidDrawDamagedArea() {
+    current_damage_ = DamageAccumulator();
+    has_damage_from_contributing_content_ = false;
+  }
   void AddDamageNextUpdate(const gfx::Rect& dmg) { current_damage_.Union(dmg); }
 
   bool GetDamageRectIfValid(gfx::Rect* rect);
 
+  bool has_damage_from_contributing_content() const {
+    return has_damage_from_contributing_content_;
+  }
+
  private:
   DamageTracker();
 
   class DamageAccumulator {
    public:
     template <typename Type>
     void Union(const Type& rect) {
       if (!is_valid_rect_)
         return;
       if (rect.IsEmpty())
@@ skipping 80 matching lines @@
 
   LayerRectMapData& RectDataForLayer(int layer_id, bool* layer_is_new);
   SurfaceRectMapData& RectDataForSurface(uint64_t surface_id,
                                          bool* layer_is_new);
 
   SortedRectMapForLayers rect_history_for_layers_;
   SortedRectMapForSurfaces rect_history_for_surfaces_;
 
   unsigned int mailboxId_;
   DamageAccumulator current_damage_;
+  // Damage from contributing render surface and layer
+  bool has_damage_from_contributing_content_;
 
   // Damage accumulated since the last call to PrepareForUpdate().
   DamageAccumulator damage_for_this_update_;
 
   DISALLOW_COPY_AND_ASSIGN(DamageTracker);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_DAMAGE_TRACKER_H_