Material and RaisedButton.

sky/sdk/lib/framework/widgets/ui_node.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:async';
 import 'dart:collection';
 import 'dart:mirrors';
 import 'dart:sky' as sky;
 
 import '../app.dart';
@@ skipping 737 matching lines @@
 class UINodeAppView extends AppView {
 
   UINodeAppView({ RenderView renderViewOverride: null })
       : super(renderViewOverride: renderViewOverride) {
     assert(_appView == null);
   }
 
   static UINodeAppView _appView;
   static AppView get appView => _appView;
   static void initUINodeAppView({ RenderView renderViewOverride: null }) {
-    _appView = new UINodeAppView(renderViewOverride: renderViewOverride);
+    if (_appView == null)
+      _appView = new UINodeAppView(renderViewOverride: renderViewOverride);
   }
 
   void dispatchEvent(sky.Event event, HitTestResult result) {
     assert(_appView == this);
     super.dispatchEvent(event, result);
     for (HitTestEntry entry in result.path.reversed) {
       UINode target = RenderObjectWrapper._getMounted(entry.target);
       if (target == null)
         continue;
       RenderObject targetRoot = target.root;
@@ skipping 81 matching lines @@
       // we haven't attached it yet
       assert(_container.child == null);
       _container.child = root;
     }
     assert(root.parent == _container);
   }
 
   UINode build() => builder();
 
 }