Keeping track of descendants that draw content instead of recalcualting

cc/layers/picture_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/picture_layer.h"
 
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/picture_layer_impl.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "third_party/skia/include/core/SkPictureRecorder.h"
@@ skipping 10 matching lines @@
       pile_(make_scoped_refptr(new PicturePile())),
       instrumentation_object_tracker_(id()),
       is_mask_(false),
       update_source_frame_number_(-1),
       can_use_lcd_text_last_frame_(can_use_lcd_text()) {
 }
 
 PictureLayer::~PictureLayer() {
 }
 
-bool PictureLayer::DrawsContent() const {
-  return Layer::DrawsContent() && client_;
-}
-
 scoped_ptr<LayerImpl> PictureLayer::CreateLayerImpl(LayerTreeImpl* tree_impl) {
   return PictureLayerImpl::Create(tree_impl, id()).PassAs<LayerImpl>();
 }
 
 void PictureLayer::PushPropertiesTo(LayerImpl* base_layer) {
   Layer::PushPropertiesTo(base_layer);
   PictureLayerImpl* layer_impl = static_cast<PictureLayerImpl*>(base_layer);
 
   if (layer_impl->bounds().IsEmpty()) {
     // Update may not get called for an empty layer, so resize here instead.
@@ skipping 148 matching lines @@
                          &opaque,
                          ContentLayerClient::GRAPHICS_CONTEXT_ENABLED);
   skia::RefPtr<SkPicture> picture = skia::AdoptRef(recorder.endRecording());
   return picture;
 }
 
 bool PictureLayer::IsSuitableForGpuRasterization() const {
   return pile_->is_suitable_for_gpu_rasterization();
 }
 
+void PictureLayer::ClearClient() {
+  client_ = NULL;
+  UpdateDrawsContent(HasDrawableContent());
+}
+
+bool PictureLayer::HasDrawableContent() const {
+  return client_ && Layer::HasDrawableContent();
+}
+
 void PictureLayer::RunMicroBenchmark(MicroBenchmark* benchmark) {
   benchmark->RunOnLayer(this);
 }
 
 }  // namespace cc