Transfer LayerImpl ownership to LayerTreeImpl

cc/trees/tree_synchronizer.h

Index: cc/trees/tree_synchronizer.h
diff --git a/cc/trees/tree_synchronizer.h b/cc/trees/tree_synchronizer.h
index 2e6e8f09092aa8bd0f0006e208eda8f9ffea61c2..607a4b41548f2301870edb7301a7026b2eee3da3 100644
--- a/cc/trees/tree_synchronizer.h
+++ b/cc/trees/tree_synchronizer.h
@@ -20,14 +20,8 @@ class CC_EXPORT TreeSynchronizer {
   // Accepts a Layer tree and returns a reference to a LayerImpl tree that
   // duplicates the structure of the Layer tree, reusing the LayerImpls in the
   // tree provided by old_layer_impl_root if possible.
-  static scoped_ptr<LayerImpl> SynchronizeTrees(
-      Layer* layer_root,
-      scoped_ptr<LayerImpl> old_layer_impl_root,
-      LayerTreeImpl* tree_impl);
-  static scoped_ptr<LayerImpl> SynchronizeTrees(
-      LayerImpl* layer_root,
-      scoped_ptr<LayerImpl> old_layer_impl_root,
-      LayerTreeImpl* tree_impl);
+  static void SynchronizeTrees(Layer* layer_root, LayerTreeImpl* tree_impl);
+  static void SynchronizeTrees(LayerImpl* layer_root, LayerTreeImpl* tree_impl);
 
   // Pushes properties from a Layer or LayerImpl tree to a structurally
   // equivalent LayerImpl tree.