cc: Fix resource eviction with impl-side painting.

cc/layer_tree_impl.h

Index: cc/layer_tree_impl.h
diff --git a/cc/layer_tree_impl.h b/cc/layer_tree_impl.h
index e83647b57f4a9cc5bd137f636da1731309cf047c..71f8c9bebb5ef78bed5a41dd45790e2eb84211bc 100644
--- a/cc/layer_tree_impl.h
+++ b/cc/layer_tree_impl.h
@@ -137,6 +137,10 @@ class CC_EXPORT LayerTreeImpl {
 
   void DidBecomeActive();
 
+  bool ContentsTexturesPurged() const;
+  void SetContentsTexturesPurged();
+  void ResetContentsTexturesPurged();
+
 protected:
   LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl);
 
@@ -159,6 +163,8 @@ protected:
   // rendering and input event hit testing.
   LayerList render_surface_layer_list_;
 
+  bool contents_textures_purged_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };