Keeping track of descendants that draw content instead of recalcualting

cc/trees/layer_tree_host_common_unittest.cc

 // Copyright 2011 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/trees/layer_tree_host_common.h"
 
 #include <set>
 
 #include "cc/animation/layer_animation_controller.h"
 #include "cc/animation/transform_operations.h"
@@ skipping 6967 matching lines @@
 
   child2->Set3dSortingContextId(1);
   child3->Set3dSortingContextId(1);
 
   child2->AddChild(child3.Pass());
   child1->AddChild(child2.Pass());
   root->AddChild(child1.Pass());
 
   {
     LayerImplList render_surface_layer_list;
+    FakeLayerTreeHostImpl::RecursiveUpdateNumChildren(root.get());
     LayerTreeHostCommon::CalcDrawPropsImplInputsForTesting inputs(
         root.get(), root->bounds(), &render_surface_layer_list);
     inputs.can_render_to_separate_surface = true;
     LayerTreeHostCommon::CalculateDrawProperties(&inputs);
 
     EXPECT_EQ(2u, render_surface_layer_list.size());
   }
 
   {
     LayerImplList render_surface_layer_list;
@@ skipping 1595 matching lines @@
   EXPECT_FLOAT_EQ(4.f,
                   child1_layer->replica_layer()
                       ->mask_layer()
                       ->draw_properties()
                       .device_scale_factor);
   EXPECT_FLOAT_EQ(4.f, child2_layer->draw_properties().device_scale_factor);
 }
 
 }  // namespace
 }  // namespace cc