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);

[danakj, 2014/07/17 17:21:25]

It's unfortunate to require adding a virtual on LayerImpl just for unit tests
like this.

Are there actually tests that require this HasDelegatedContent on the impl side?
Seems like you're testing this behaviour on the main thread already.

[awoloszyn, 2014/07/17 20:45:00]

I reworked the RecursiveUpdateNumChildren to behave the same as the original so
we no longer need a virtual NumDescendantsThatDrawContent.

+}
+
+void FakeLayerTreeHostImpl::UpdateDrawProperties() {

[danakj, 2014/07/17 17:21:25]

Let's name this to be more clear what it does from callsites.
UpdateNumChildrenAndDrawPropertiesForActiveTree?

[awoloszyn, 2014/07/17 20:45:00]

Done.

+  UpdateNumChildrenAndDrawProperties(active_tree());
+}
+
+void FakeLayerTreeHostImpl::UpdateNumChildrenAndDrawProperties(
+    LayerTreeImpl* layerTree) {
+  RecursiveUpdateNumChildren(layerTree->root_layer());
+  layerTree->UpdateDrawProperties();
+}
+
 }  // namespace cc