[Effen] Make the drawer not be included in the build output when the drawer is not shown.

sky/examples/stocks/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/components/action_bar.dart';
 import 'package:sky/framework/components/drawer.dart';
 import 'package:sky/framework/components/drawer_header.dart';
 import 'package:sky/framework/components/floating_action_button.dart';
 import 'package:sky/framework/components/icon.dart';
 import 'package:sky/framework/components/icon_button.dart';
 import 'package:sky/framework/components/input.dart';
 import 'package:sky/framework/components/menu_divider.dart';
 import 'package:sky/framework/components/menu_item.dart';
 import 'package:sky/framework/components/modal_overlay.dart';
 import 'package:sky/framework/components/popup_menu.dart';
 import 'package:sky/framework/components/scaffold.dart';
 import 'package:sky/framework/fn.dart';
 import 'package:sky/framework/theme/typography.dart' as typography;
 import 'package:sky/framework/theme/colors.dart';
 import 'stock_data.dart';
 import 'stock_list.dart';
 import 'stock_menu.dart';
 
 import 'dart:async';
 import 'package:sky/framework/layout.dart';
 
 const bool debug = false; // set to true to dump the DOM for debugging purposes
 
 class StocksApp extends App {
-  DrawerController _drawerController = new DrawerController();
-  PopupMenuController _menuController;
 
   static final Style _actionBarStyle = new Style('''
     background-color: ${Purple[500]};''');
 
   static final Style _searchBarStyle = new Style('''
     background-color: ${Grey[50]};''');
 
   static final Style _titleStyle = new Style('''
     ${typography.white.title};''');
 
   List<Stock> _stocks = [];
-  bool _isSearching = false;
-  String _searchQuery;
 
   StocksApp() : super() {
     if (debug)
       new Timer(new Duration(seconds: 1), dumpState);
     new StockDataFetcher((StockData data) {
       setState(() {
         data.appendTo(_stocks);
       });
     });
+    _drawerController = new DrawerController(_handleDrawerStatusChanged);
   }
 
+  bool _isSearching = false;
+  String _searchQuery;
+
   void _handleSearchBegin(_) {
     setState(() {
       _isSearching = true;
     });
   }
 
   void _handleSearchEnd(_) {
     setState(() {
       _isSearching = false;
       _searchQuery = null;
     });
   }
 
   void _handleSearchQueryChanged(String query) {
     setState(() {
       _searchQuery = query;
     });
   }
 
+  DrawerController _drawerController;
+  bool _drawerShowing = false;
+
+  void _handleDrawerStatusChanged(bool showing) {
+    setState(() {
+      _drawerShowing = showing;
+    });
+  }
+
+  PopupMenuController _menuController;
+
   void _handleMenuShow(_) {
     setState(() {
       _menuController = new PopupMenuController();
       _menuController.open();
     });
   }
 
   void _handleMenuHide(_) {
     setState(() {
       _menuController.close().then((_) {
@@ skipping 75 matching lines @@
 
   UINode build() {
     List<UINode> overlays = [];
     addMenuToOverlays(overlays);
 
     return new Scaffold(
       header: _isSearching ? buildSearchBar() : buildActionBar(),
       content: new Stocklist(stocks: _stocks, query: _searchQuery),
       fab: new FloatingActionButton(
         content: new Icon(type: 'content/add_white', size: 24), level: 3),
-      drawer: buildDrawer(),
+      drawer: _drawerShowing ? buildDrawer() : null,
       overlays: overlays
     );
   }
 }