Material light and dark themes for Sky widgets

sky/examples/stocks2/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/theme/colors.dart' as colors;
-import 'package:sky/theme/typography.dart' as typography;
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/drawer.dart';
 import 'package:sky/widgets/drawer_header.dart';
 import 'package:sky/widgets/floating_action_button.dart';
 import 'package:sky/widgets/icon.dart';
 import 'package:sky/widgets/icon_button.dart';
 import 'package:sky/widgets/menu_divider.dart';
 import 'package:sky/widgets/menu_item.dart';
 import 'package:sky/widgets/modal_overlay.dart';
 import 'package:sky/widgets/navigator.dart';
@@ skipping 136 matching lines @@
     navigator.pushState("/drawer", (_) {
       _drawerController.close();
     });
   }
 
   Widget buildToolBar() {
     return new ToolBar(
         left: new IconButton(
           icon: 'navigation/menu_white',
           onPressed: _handleOpenDrawer),
-        center: new Text('Stocks', style: typography.white.title),
+        center: new Text('Stocks'),
         right: [
           new IconButton(
             icon: 'action/search_white',
             onPressed: _handleSearchBegin),
           new IconButton(
             icon: 'navigation/more_vert_white',
             onPressed: _handleMenuShow)
         ]
       );
   }
@@ skipping 32 matching lines @@
         floatingActionButton: new FloatingActionButton(
           child: new Icon(type: 'content/add_white', size: 24)
         ),
         drawer: _drawerShowing ? buildDrawer() : null
       ),
     ];
     addMenuToOverlays(overlays);
     return new Stack(overlays);
   }
 }