Keeping track of descendants that draw content instead of recalcualting

cc/test/fake_layer_tree_host_impl.cc

 // Copyright 2012 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_layer_tree_host_impl.h"
 #include "cc/test/test_shared_bitmap_manager.h"
 #include "cc/trees/layer_tree_impl.h"
 
 namespace cc {
 
@@ skipping 36 matching lines @@
   if (current_frame_time_ticks_.is_null())
     return LayerTreeHostImpl::CurrentFrameTimeTicks();
   return current_frame_time_ticks_;
 }
 
 void FakeLayerTreeHostImpl::SetCurrentFrameTimeTicks(
     base::TimeTicks current_frame_time_ticks) {
   current_frame_time_ticks_ = current_frame_time_ticks;
 }
 
+int FakeLayerTreeHostImpl::RecursiveUpdateNumChildren(LayerImpl* layer) {
+  int num_children_that_draw_content = 0;
+  for (size_t i = 0; i < layer->children().size(); ++i) {
+    num_children_that_draw_content +=
+        RecursiveUpdateNumChildren(layer->children()[i]);
+  }
+  layer->SetNumDescendantsThatDrawContent(num_children_that_draw_content);
+  return num_children_that_draw_content + (layer->DrawsContent() ? 1 : 0) +
+         (layer->HasDelegatedContent() ? 1000 : 0);
+}
+
+void FakeLayerTreeHostImpl::UpdateDrawProperties() {
+  FakeSyncDrawProperties(active_tree());
+  active_tree()->UpdateDrawProperties();
+}
+
+void FakeLayerTreeHostImpl::FakeSyncDrawProperties(LayerTreeImpl* layerTree) {
+  RecursiveUpdateNumChildren(layerTree->root_layer());
+  layerTree->UpdateDrawProperties();
+}
+
 }  // namespace cc