Fix build after hixie's rename

sky/examples/fn2/container.dart

 // Copyright 2015 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.
 
 import 'dart:sky' as sky;
 import 'package:sky/framework/fn2.dart';
 import 'package:sky/framework/rendering/box.dart';
 import '../lib/solid_color_box.dart';
 
-class Rectangle extends RenderNodeWrapper {
+class Rectangle extends RenderObjectWrapper {
   RenderSolidColorBox root;
   RenderSolidColorBox createNode() =>
       new RenderSolidColorBox(color, desiredSize: new sky.Size(40.0, 130.0));
 
   final int color;
 
   Rectangle(this.color, { Object key }) : super(key: key);
 }
 
 class ContainerApp extends App {
@@ skipping 26 matching lines @@
   }
 
   void _handleGestureTap(sky.GestureEvent event) {
     print("_handleGestureTap");
   }
 }
 
 void main() {
   new ContainerApp();
 }