Keeping track of descendants that draw content instead of recalcualting

cc/layers/ui_resource_layer.cc

 // Copyright 2013 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/ui_resource_layer.h"
 
 #include "cc/layers/ui_resource_layer_impl.h"
 #include "cc/resources/prioritized_resource.h"
 #include "cc/resources/resource_update.h"
 #include "cc/resources/resource_update_queue.h"
@@ skipping 95 matching lines @@
     return;
 
   Layer::SetLayerTreeHost(host);
 
   // Recreate the resource hold against the new LTH.
   RecreateUIResourceHolder();
 }
 
 void UIResourceLayer::RecreateUIResourceHolder() {
   ui_resource_holder_.reset();
-  if (!layer_tree_host() || bitmap_.empty())
-    return;
-
-  ui_resource_holder_ =
-    ScopedUIResourceHolder::Create(layer_tree_host(), bitmap_);
+  if (layer_tree_host() && !bitmap_.empty()) {
+    ui_resource_holder_ =
+        ScopedUIResourceHolder::Create(layer_tree_host(), bitmap_);
+  }
+  UpdateDrawsContent(HasDrawableContent());
 }
 
 void UIResourceLayer::SetBitmap(const SkBitmap& skbitmap) {
   bitmap_ = skbitmap;
 
   RecreateUIResourceHolder();
   SetNeedsCommit();
 }
 
 void UIResourceLayer::SetUIResourceId(UIResourceId resource_id) {
   if (ui_resource_holder_ && ui_resource_holder_->id() == resource_id)
     return;
 
   if (resource_id) {
     ui_resource_holder_ = SharedUIResourceHolder::Create(resource_id);
   } else {
     ui_resource_holder_.reset();
   }
 
+  UpdateDrawsContent(HasDrawableContent());
   SetNeedsCommit();
 }
 
-bool UIResourceLayer::DrawsContent() const {
+bool UIResourceLayer::HasDrawableContent() const {
   return ui_resource_holder_ && ui_resource_holder_->id() &&
-         Layer::DrawsContent();
+         Layer::HasDrawableContent();
 }
 
 void UIResourceLayer::PushPropertiesTo(LayerImpl* layer) {
   Layer::PushPropertiesTo(layer);
   UIResourceLayerImpl* layer_impl = static_cast<UIResourceLayerImpl*>(layer);
 
   if (!ui_resource_holder_) {
     layer_impl->SetUIResourceId(0);
   } else {
     DCHECK(layer_tree_host());
 
     gfx::Size image_size =
         layer_tree_host()->GetUIResourceSize(ui_resource_holder_->id());
     layer_impl->SetUIResourceId(ui_resource_holder_->id());
     layer_impl->SetImageBounds(image_size);
     layer_impl->SetUV(uv_top_left_, uv_bottom_right_);
     layer_impl->SetVertexOpacity(vertex_opacity_);
   }
 }
 
 }  // namespace cc