Keeping track of descendants that draw content instead of recalcualting

cc/layers/delegated_renderer_layer.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/layers/delegated_renderer_layer.h"
 
 #include "cc/layers/delegated_renderer_layer_impl.h"
 #include "cc/output/delegated_frame_data.h"
 #include "cc/quads/render_pass_draw_quad.h"
 #include "cc/trees/blocking_task_runner.h"
@@ skipping 80 matching lines @@
     return updated;
 
   frame_data_ =
       frame_provider_->GetFrameDataAndRefResources(this, &frame_damage_);
   should_collect_new_frame_ = false;
 
   SetNeedsPushProperties();
   return true;
 }
 
+bool DelegatedRendererLayer::HasDelegatedContent() const {
+  return true;
+}
+
 }  // namespace cc