Wire up popup menus to back button

sky/sdk/example/stocks/lib/stock_home.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/editing/input.dart';
 import 'package:sky/animation/animation_performance.dart';
 import 'package:sky/widgets/animated_component.dart';
 import 'package:sky/widgets/animation_builder.dart';
 import 'package:sky/theme/colors.dart' as colors;
 import 'package:sky/widgets/basic.dart';
@@ skipping 288 matching lines @@
     return widget;
   }
 
   void addMenuToOverlays(List<Widget> overlays) {
     if (_menuStatus == PopupMenuStatus.inactive)
       return;
     overlays.add(new ModalOverlay(
       children: [new StockMenu(
         showing: _menuShowing,
         onStatusChanged: _handleMenuStatusChanged,
+        navigator: navigator,
         autorefresh: _autorefresh,
         onAutorefreshChanged: _handleAutorefreshChanged
       )],
       onDismiss: _handleMenuHide));
   }
 
   Widget build() {
     List<Widget> overlays = [
       new Scaffold(
         toolbar: _isSearching ? buildSearchBar() : buildToolBar(),
         body: buildTabNavigator(),
         snackBar: buildSnackBar(),
         floatingActionButton: buildFloatingActionButton(),
         drawer: buildDrawer()
       ),
     ];
     addMenuToOverlays(overlays);
     return new Stack(overlays);
   }
 }