Keeping track of descendants that draw content instead of recalcualting

cc/layers/heads_up_display_layer.cc

Index: cc/layers/heads_up_display_layer.cc
diff --git a/cc/layers/heads_up_display_layer.cc b/cc/layers/heads_up_display_layer.cc
index ca63471e303d9a97271e2d280d2c4f6abbc5ea9e..6adf8d06ff200de54342ed6c35649fd11b65fb62 100644
--- a/cc/layers/heads_up_display_layer.cc
+++ b/cc/layers/heads_up_display_layer.cc
@@ -16,7 +16,10 @@ scoped_refptr<HeadsUpDisplayLayer> HeadsUpDisplayLayer::Create() {
   return make_scoped_refptr(new HeadsUpDisplayLayer());
 }
 
-HeadsUpDisplayLayer::HeadsUpDisplayLayer() {}
+HeadsUpDisplayLayer::HeadsUpDisplayLayer() {
+  SetIsDrawable(true);
+  UpdateDrawsContent(HasDrawableContent());
+}
 
 HeadsUpDisplayLayer::~HeadsUpDisplayLayer() {}
 
@@ -47,7 +50,9 @@ void HeadsUpDisplayLayer::PrepareForCalculateDrawProperties(
   SetTransform(matrix);
 }
 
-bool HeadsUpDisplayLayer::DrawsContent() const { return true; }
+bool HeadsUpDisplayLayer::HasDrawableContent() const {
+  return true;
+}
 
 scoped_ptr<LayerImpl> HeadsUpDisplayLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {