Keeping track of descendants that draw content instead of recalcualting

cc/test/fake_delegated_renderer_layer_impl.cc

 // 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.
 
 #include "cc/test/fake_delegated_renderer_layer_impl.h"
 
 #include "base/bind.h"
 #include "cc/output/delegated_frame_data.h"
 #include "cc/quads/draw_quad.h"
 #include "cc/resources/returned_resource.h"
@@ skipping 52 matching lines @@
       base::Bind(&AddResourceToFrame, resource_provider, delegated_frame.get());
   for (size_t i = 0; i < delegated_frame->render_pass_list.size(); ++i) {
     RenderPass* pass = delegated_frame->render_pass_list[i];
     for (size_t j = 0; j < pass->quad_list.size(); ++j)
       pass->quad_list[j]->IterateResources(add_resource_to_frame_callback);
   }
 
   CreateChildIdIfNeeded(base::Bind(&NoopReturnCallback));
   SetFrameData(delegated_frame.get(), gfx::RectF());
 }
+int FakeDelegatedRendererLayerImpl::NumDescendantsThatDrawContent() const {
+  return 1000;
+}
 
 }  // namespace cc