Abstract out the AppView logic in fn so that it can also be used in non-pure-fn apps.

sky/examples/stocks2/lib/stock_app.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 'package:sky/framework/components2/tool_bar.dart';
 import 'package:sky/framework/components2/drawer.dart';
 import 'package:sky/framework/components2/drawer_header.dart';
 import 'package:sky/framework/components2/floating_action_button.dart';
 import 'package:sky/framework/components2/icon.dart';
 import 'package:sky/framework/components2/icon_button.dart';
@@ skipping 28 matching lines @@
     // if (debug)
     //   new Timer(new Duration(seconds: 1), dumpState);
     new StockDataFetcher((StockData data) {
       setState(() {
         data.appendTo(_stocks);
       });
     });
     _drawerController = new DrawerController(_handleDrawerStatusChanged);
   }
 
-  void syncFields(StocksApp source) { }
-
   bool _isSearching = false;
   String _searchQuery;
 
   void _handleSearchBegin(_) {
     setState(() {
       _isSearching = true;
     });
   }
 
   void _handleSearchEnd(_) {
@@ skipping 156 matching lines @@
 }
 
 void main() {
   print("starting stocks app!");
   App app = new StocksApp();
   app.appView.onFrame = () {
     // uncomment this for debugging:
     // app.appView.debugDumpRenderTree();
   };
 }