(not for review yet)

cc/trees/layer_tree_impl.h

 // Copyright 2012 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_IMPL_H_
 #define CC_TREES_LAYER_TREE_IMPL_H_
 
 #include <list>
 #include <string>
 #include <vector>
@@ skipping 161 matching lines @@
   // These should be called by LayerImpl's ctor/dtor.
   void RegisterLayer(LayerImpl* layer);
   void UnregisterLayer(LayerImpl* layer);
 
   AnimationRegistrar* animationRegistrar() const;
 
   void PushPersistedState(LayerTreeImpl* pending_tree);
 
   void DidBecomeActive();
 
+  void SetUIResourceEvictionCountAcked(uint64 ui_resource_eviction_count_acked);
+  uint64 ui_resource_eviction_count_acked() const {
+    return ui_resource_eviction_count_acked_;
+  }
+
   bool ContentsTexturesPurged() const;
   void SetContentsTexturesPurged();
   void ResetContentsTexturesPurged();
 
   // Set on the active tree when the viewport size recently changed
   // and the active tree's size is now out of date.
   bool ViewportSizeInvalid() const;
   void SetViewportSizeInvalid();
   void ResetViewportSizeInvalid();
 
@@ skipping 44 matching lines @@
 
   std::vector<LayerImpl*> layers_with_copy_output_request_;
 
   // Persisted state for non-impl-side-painting.
   int scrolling_layer_id_from_previous_tree_;
 
   // List of visible layers for the most recently prepared frame. Used for
   // rendering and input event hit testing.
   LayerImplList render_surface_layer_list_;
 
+  // The UI resource eviction count most recently acked. This value is updated
+  // through ProcessUIResourceRequestQueue. If this value is not equal to
+  // |layer_tree_host_impl_|'s UI resource eviction count, then this tree may
+  // may reference evicted UI resources and cannot be drawn.
+  uint64 ui_resource_eviction_count_acked_;
+
   bool contents_textures_purged_;
   bool viewport_size_invalid_;
   bool needs_update_draw_properties_;
 
   // In impl-side painting mode, this is true when the tree may contain
   // structural differences relative to the active tree.
   bool needs_full_tree_sync_;
 
   ui::LatencyInfo latency_info_;
 
   UIResourceRequestQueue ui_resource_request_queue_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_IMPL_H_