Transfer LayerImpl ownership to LayerTreeImpl

cc/trees/layer_tree_host.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/layer_tree_host.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 353 matching lines @@
 
   LayerTreeImpl* sync_tree = host_impl->sync_tree();
 
   if (next_commit_forces_redraw_) {
     sync_tree->ForceRedrawNextActivation();
     next_commit_forces_redraw_ = false;
   }
 
   sync_tree->set_source_frame_number(source_frame_number());
 
-  if (needs_full_tree_sync_) {
-    sync_tree->SetRootLayer(TreeSynchronizer::SynchronizeTrees(
-        root_layer(), sync_tree->DetachLayerTree(), sync_tree));
-  }
+  if (needs_full_tree_sync_)
+    TreeSynchronizer::SynchronizeTrees(root_layer(), sync_tree);
+
   sync_tree->set_needs_full_tree_sync(needs_full_tree_sync_);
   needs_full_tree_sync_ = false;
 
   if (hud_layer_.get()) {
     LayerImpl* hud_impl = LayerTreeHostCommon::FindLayerInSubtree(
         sync_tree->root_layer(), hud_layer_->id());
     sync_tree->set_hud_layer(static_cast<HeadsUpDisplayLayerImpl*>(hud_impl));
   } else {
     sync_tree->set_hud_layer(NULL);
   }
@@ skipping 1189 matching lines @@
   LayerTreeHostCommon::CallFunctionForSubtree(
       root_layer(), [seq_num](Layer* layer) {
         layer->set_property_tree_sequence_number(seq_num);
       });
 
   surface_id_namespace_ = proto.surface_id_namespace();
   next_surface_sequence_ = proto.next_surface_sequence();
 }
 
 }  // namespace cc