Make back button control drawer in stocks app

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/rendering/sky_binding.dart';
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/navigator.dart';
 import 'package:sky/widgets/widget.dart';
 
+import 'stock_data.dart';
 import 'stock_home.dart';
 import 'stock_settings.dart';
 
 class StocksApp extends App {
 
-  NavigationState _navState = new NavigationState([
-    new Route(name: '/', builder: (navigator) => new StockHome(navigator)),
-    new Route(name: '/settings', builder: (navigator) => new StockSettings(navigator)),
-  ]);
+  StocksApp() {
+    _navigationState = new NavigationState([
+      new Route(
+        name: '/', 
+        builder: (navigator, route) => new StockHome(navigator, route, _stocks)
+      ),
+      new Route(
+        name: '/settings',
+        builder: (navigator, route) => new StockSettings(navigator)
+      ),
+    ]);
+  }
+
+  void didMount() {
+    new StockDataFetcher((StockData data) {
+      setState(() {
+        data.appendTo(_stocks);
+      });
+    });
+  }
+
+  final List<Stock> _stocks = [];
+  NavigationState _navigationState;
 
   void onBack() {
-    if (_navState.hasPrevious()) {
-      setState(() {
-        _navState.pop();
-      });
-      return;
-    }
-    print ("Should exit app here");
+    setState(() {
+      _navigationState.pop();
+    });
     // TODO(jackson): Need a way to invoke default back behavior here
   }
 
   Widget build() {
-    return new Navigator(_navState);
+    return new Navigator(_navigationState);
   }
 }
 
 void main() {
   print("starting stocks app!");
   runApp(new StocksApp());
   SkyBinding.instance.onFrame = () {
     // uncomment this for debugging:
     // SkyBinding.instance.debugDumpRenderTree();
   };
 }