Keeping track of descendants that draw content instead of recalcualting

cc/layers/content_layer.h

Index: cc/layers/content_layer.h
diff --git a/cc/layers/content_layer.h b/cc/layers/content_layer.h
index 9bef22bb704728015360a4b3351ac7dfa5f2bc77..c440c6fa11c1350656e428fc4edf63cbb6c0166f 100644
--- a/cc/layers/content_layer.h
+++ b/cc/layers/content_layer.h
@@ -38,9 +38,8 @@ class CC_EXPORT ContentLayer : public TiledLayer {
  public:
   static scoped_refptr<ContentLayer> Create(ContentLayerClient* client);
 
-  void ClearClient() { client_ = NULL; }
+  void ClearClient();
 
-  virtual bool DrawsContent() const OVERRIDE;
   virtual void SetLayerTreeHost(LayerTreeHost* layer_tree_host) OVERRIDE;
   virtual void SetTexturePriorities(const PriorityCalculator& priority_calc)
       OVERRIDE;
@@ -60,6 +59,8 @@ class CC_EXPORT ContentLayer : public TiledLayer {
   explicit ContentLayer(ContentLayerClient* client);
   virtual ~ContentLayer();
 
+  virtual bool HasDrawableContent() const OVERRIDE;
+
   // TiledLayer implementation.
   virtual LayerUpdater* Updater() const OVERRIDE;