cc: Clean up root_layer code in LTI

cc/trees/tree_synchronizer.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/trees/tree_synchronizer.h"
 
 #include <stddef.h>
 
 #include <set>
 
@@ skipping 66 matching lines @@
                    LayerTreeType* host,
                    LayerTreeImpl* tree_impl) {
   tree_impl->ClearLayerList();
   for (auto* layer : *host) {
     std::unique_ptr<LayerImpl> layer_impl(
         ReuseOrCreateLayerImpl(old_layers, layer, tree_impl));
 
     tree_impl->AddToLayerList(layer_impl.get());
     tree_impl->AddLayer(std::move(layer_impl));
   }
-  tree_impl->SetRootLayerFromLayerList();
+  tree_impl->OnCanDrawStateChangedForTree();
 }
 
 template <typename LayerType>
 static void PushLayerPropertiesInternal(
     std::unordered_set<LayerType*> layers_that_should_push_properties,
     LayerTreeImpl* impl_tree) {
   for (auto layer : layers_that_should_push_properties) {
     LayerImpl* layer_impl = impl_tree->LayerById(layer->id());
     DCHECK(layer_impl);
     layer->PushPropertiesTo(layer_impl);
   }
 }
 
 void TreeSynchronizer::PushLayerProperties(LayerTreeImpl* pending_tree,
                                            LayerTreeImpl* active_tree) {
   PushLayerPropertiesInternal(pending_tree->LayersThatShouldPushProperties(),
                               active_tree);
 }
 
 void TreeSynchronizer::PushLayerProperties(LayerTreeHost* host_tree,
                                            LayerTreeImpl* impl_tree) {
   PushLayerPropertiesInternal(host_tree->LayersThatShouldPushProperties(),
                               impl_tree);
 }
 
 }  // namespace cc