Keeping track of descendants that draw content instead of recalcualting

cc/test/fake_layer_tree_host_impl.cc

Index: cc/test/fake_layer_tree_host_impl.cc
diff --git a/cc/test/fake_layer_tree_host_impl.cc b/cc/test/fake_layer_tree_host_impl.cc
index 7361794e7b1aa707018c8fe3a0f6214f5863ada6..d8b238d016742a9cc4c06eb21a82e63ed4706ee6 100644
--- a/cc/test/fake_layer_tree_host_impl.cc
+++ b/cc/test/fake_layer_tree_host_impl.cc
@@ -54,4 +54,25 @@ void FakeLayerTreeHostImpl::SetCurrentFrameTimeTicks(
   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