Keeping track of descendants that draw content instead of recalcualting

cc/layers/io_surface_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/io_surface_layer.h"
 
 #include "cc/layers/io_surface_layer_impl.h"
 
 namespace cc {
 
 scoped_refptr<IOSurfaceLayer> IOSurfaceLayer::Create() {
   return make_scoped_refptr(new IOSurfaceLayer());
 }
 
 IOSurfaceLayer::IOSurfaceLayer() : Layer(), io_surface_id_(0) {}
 
 IOSurfaceLayer::~IOSurfaceLayer() {}
 
 void IOSurfaceLayer::SetIOSurfaceProperties(uint32_t io_surface_id,
                                             const gfx::Size& size) {
   io_surface_id_ = io_surface_id;
   io_surface_size_ = size;
+  UpdateDrawsContent(true);
   SetNeedsCommit();
 }
 
 scoped_ptr<LayerImpl> IOSurfaceLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
   return IOSurfaceLayerImpl::Create(tree_impl, layer_id_).PassAs<LayerImpl>();
 }
 
-bool IOSurfaceLayer::DrawsContent() const {
-  return io_surface_id_ && Layer::DrawsContent();
+void IOSurfaceLayer::UpdateDrawsContent(bool draws_content) {
+  Layer::UpdateDrawsContent(draws_content && io_surface_id_);
 }
 
 void IOSurfaceLayer::PushPropertiesTo(LayerImpl* layer) {
   Layer::PushPropertiesTo(layer);
 
   IOSurfaceLayerImpl* io_surface_layer =
       static_cast<IOSurfaceLayerImpl*>(layer);
   io_surface_layer->SetIOSurfaceProperties(io_surface_id_, io_surface_size_);
 }
 
 bool IOSurfaceLayer::Update(ResourceUpdateQueue* queue,
                             const OcclusionTracker<Layer>* occlusion) {
   bool updated = Layer::Update(queue, occlusion);
 
   // This layer doesn't update any resources from the main thread side,
   // but repaint rects need to be sent to the layer impl via commit.
   return updated || !update_rect_.IsEmpty();
 }
 
 }  // namespace cc