Keeping track of descendants that draw content instead of recalcualting

cc/test/fake_delegated_renderer_layer_impl.h

 // Copyright 2013 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_TEST_FAKE_DELEGATED_RENDERER_LAYER_IMPL_H_
 #define CC_TEST_FAKE_DELEGATED_RENDERER_LAYER_IMPL_H_
 
 #include "cc/layers/delegated_renderer_layer_impl.h"
 
 namespace cc {
@@ skipping 10 matching lines @@
       OVERRIDE;
 
   int ChildId() const { return ChildIdForTesting(); }
   const RenderPassList& RenderPassesInDrawOrder() const {
     return RenderPassesInDrawOrderForTesting();
   }
   ResourceProvider::ResourceIdSet Resources() const;
 
   void SetFrameDataForRenderPasses(float device_scale_factor,
                                    RenderPassList* pass_list);
+  virtual int NumDescendantsThatDrawContent() const OVERRIDE;
 
  protected:
   FakeDelegatedRendererLayerImpl(LayerTreeImpl* tree_impl, int id);
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_FAKE_DELEGATED_RENDERER_LAYER_IMPL_H_