Keeping track of descendants that draw content instead of recalcualting

cc/layers/content_layer.cc

 // Copyright 2010 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/content_layer.h"
 
 #include "base/auto_reset.h"
 #include "base/metrics/histogram.h"
 #include "base/time/time.h"
 #include "cc/layers/content_layer_client.h"
@@ skipping 27 matching lines @@
 }
 
 ContentLayer::ContentLayer(ContentLayerClient* client)
     : TiledLayer(),
       client_(client),
       can_use_lcd_text_last_frame_(can_use_lcd_text()) {
 }
 
 ContentLayer::~ContentLayer() {}
 
-bool ContentLayer::DrawsContent() const {
-  return TiledLayer::DrawsContent() && client_;
+void ContentLayer::ClearClient() {
+  client_ = NULL;
+  UpdateDrawsContent(HasDrawableContent());
+}
+
+bool ContentLayer::HasDrawableContent() const {
+  return client_ && TiledLayer::HasDrawableContent();
 }
 
 void ContentLayer::SetLayerTreeHost(LayerTreeHost* host) {
   TiledLayer::SetLayerTreeHost(host);
 
   if (!updater_.get())
     return;
 
   if (host) {
     updater_->set_rendering_stats_instrumentation(
@@ skipping 94 matching lines @@
   return picture;
 }
 
 void ContentLayer::OnOutputSurfaceCreated() {
   SetTextureFormat(
       layer_tree_host()->GetRendererCapabilities().best_texture_format);
   TiledLayer::OnOutputSurfaceCreated();
 }
 
 }  // namespace cc