cc: Add id->LayerImpl map to LayerTreeImpl

cc/layer_tree_impl.cc

 // Copyright 2011 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/layer_tree_impl.h"
 
 #include "cc/layer_tree_host_common.h"
 #include "cc/layer_tree_host_impl.h"
 
 namespace cc {
 
 LayerTreeImpl::LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl)
     : layer_tree_host_impl_(layer_tree_host_impl)
     , source_frame_number_(-1)
     , hud_layer_(0)
     , root_scroll_layer_(0)
     , currently_scrolling_layer_(0)
     , scrolling_layer_id_from_previous_tree_(0) {
 }
 
 LayerTreeImpl::~LayerTreeImpl() {
+  // Need to explicitly clear the tree prior to destroying this so that
+  // the LayerTreeImpl pointer is still valid in the LayerImpl dtor.
+  root_layer_.reset();
 }
 
 static LayerImpl* findRootScrollLayer(LayerImpl* layer)
 {
     if (!layer)
         return 0;
 
     if (layer->scrollable())
         return layer;
 
@@ skipping 29 matching lines @@
   currently_scrolling_layer_ = NULL;
 
   return root_layer_.Pass();
 }
 
 void LayerTreeImpl::ClearCurrentlyScrollingLayer() {
   currently_scrolling_layer_ = NULL;
   scrolling_layer_id_from_previous_tree_ = 0;
 }
 
+LayerImpl* LayerTreeImpl::LayerById(int id) {
+  LayerIdMap::iterator iter = layer_id_map_.find(id);
+  return iter != layer_id_map_.end() ? iter->second : NULL;
+}
+
+void LayerTreeImpl::RegisterLayer(LayerImpl* layer) {
+  DCHECK(!LayerById(layer->id()));
+  layer_id_map_[layer->id()] = layer;
+}
+
+void LayerTreeImpl::UnregisterLayer(LayerImpl* layer) {
+  DCHECK(LayerById(layer->id()));
+  layer_id_map_.erase(layer->id());
+}
+
 const LayerTreeSettings& LayerTreeImpl::settings() const {
   return layer_tree_host_impl_->settings();
 }
 
 OutputSurface* LayerTreeImpl::output_surface() const {
   return layer_tree_host_impl_->outputSurface();
 }
 
 ResourceProvider* LayerTreeImpl::resource_provider() const {
   return layer_tree_host_impl_->resourceProvider();
@@ skipping 34 matching lines @@
 std::string LayerTreeImpl::layer_tree_as_text() const {
   return layer_tree_host_impl_->layerTreeAsText();
 }
 
 DebugRectHistory* LayerTreeImpl::debug_rect_history() const {
   return layer_tree_host_impl_->debugRectHistory();
 }
 
 
 } // namespace cc