Fix the App code to use the new names for AppView.

sky/sdk/lib/widgets/widget.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 '../base/hit_test.dart';
@@ skipping 802 matching lines @@
 }
 
 abstract class App extends Component {
   void _handleEvent(sky.Event event) {
     if (event.type == 'back')
       onBack();
   }
 
   void didMount() {
     super.didMount();
-    WidgetAppView.appView.addEventListener(_handleEvent);
+    SkyBinding.instance.addEventListener(_handleEvent);
   }
 
   void didUnmount() {
     super.didUnmount();
-    WidgetAppView.appView.removeEventListener(_handleEvent);
+    SkyBinding.instance.removeEventListener(_handleEvent);
   }
 
   // Override this to handle back button behavior in your app
   void onBack() { }
 }
 
 abstract class AbstractWidgetRoot extends Component {
 
   AbstractWidgetRoot() : super(stateful: true) {
     _mounted = true;
@@ skipping 68 matching lines @@
     if (root.parent == null) {
       // we haven't attached it yet
       assert(_container.child == null);
       _container.child = root;
     }
     assert(root.parent == _container);
   }
 
   Widget build() => builder();
 }