Keeping track of descendants that draw content instead of recalcualting

cc/layers/delegated_renderer_layer.cc

Index: cc/layers/delegated_renderer_layer.cc
diff --git a/cc/layers/delegated_renderer_layer.cc b/cc/layers/delegated_renderer_layer.cc
index c47206172ceedcd205e21525f3d11d3778700d3c..2dd12344df8ed607d06b6104a88be8ff817286f6 100644
--- a/cc/layers/delegated_renderer_layer.cc
+++ b/cc/layers/delegated_renderer_layer.cc
@@ -98,4 +98,8 @@ bool DelegatedRendererLayer::Update(ResourceUpdateQueue* queue,
   return true;
 }
 
+bool DelegatedRendererLayer::HasDelegatedContent() const {
+  return true;
+}
+
 }  // namespace cc