Keeping track of descendants that draw content instead of recalcualting

cc/layers/layer_impl_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/layers/layer_impl.h"
 
 #include "cc/layers/painted_scrollbar_layer_impl.h"
 #include "cc/output/filter_operation.h"
 #include "cc/output/filter_operations.h"
 #include "cc/test/fake_impl_proxy.h"
@@ skipping 182 matching lines @@
 
   // Changing these properties should cause the layer to need to push properties
   EXECUTE_AND_VERIFY_NEEDS_PUSH_PROPERTIES_AND_SUBTREE_DID_NOT_CHANGE(
       root->SetScrollParent(scroll_parent.get()));
   EXECUTE_AND_VERIFY_NEEDS_PUSH_PROPERTIES_AND_SUBTREE_DID_NOT_CHANGE(
       root->SetScrollChildren(scroll_children));
   EXECUTE_AND_VERIFY_NEEDS_PUSH_PROPERTIES_AND_SUBTREE_DID_NOT_CHANGE(
       root->SetClipParent(clip_parent.get()));
   EXECUTE_AND_VERIFY_NEEDS_PUSH_PROPERTIES_AND_SUBTREE_DID_NOT_CHANGE(
       root->SetClipChildren(clip_children));
+  EXECUTE_AND_VERIFY_NEEDS_PUSH_PROPERTIES_AND_SUBTREE_DID_NOT_CHANGE(
+      root->SetNumDescendantsThatDrawContent(10));
 
   // After setting all these properties already, setting to the exact same
   // values again should not cause any change.
   EXECUTE_AND_VERIFY_SUBTREE_DID_NOT_CHANGE(
       root->SetTransformOrigin(arbitrary_point_3f));
   EXECUTE_AND_VERIFY_SUBTREE_DID_NOT_CHANGE(root->SetMasksToBounds(true));
   EXECUTE_AND_VERIFY_SUBTREE_DID_NOT_CHANGE(
       root->SetPosition(arbitrary_point_f));
   EXECUTE_AND_VERIFY_SUBTREE_DID_NOT_CHANGE(
       root->SetShouldFlattenTransform(false));
@@ skipping 469 matching lines @@
       layer()->id(), tree()->root_layer()->id());
 
   int expected_horizontal_maximum =
       layer()->bounds().width() - tree()->root_layer()->bounds().width();
   EXPECT_EQ(expected_horizontal_maximum, horizontal_scrollbar->maximum());
   EXPECT_EQ(scroll_offset.x(), horizontal_scrollbar->current_pos());
 }
 
 }  // namespace
 }  // namespace cc