Remove one more use of mirrors: Components now have to explicitly sync their fields.

sky/sdk/lib/framework/components2/tool_bar.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 '../fn2.dart';
 import '../theme/view_configuration.dart';
 import '../theme2/shadows.dart';
 
 class ToolBar extends Component {
 
   ToolBar({
     String key,
     this.left,
     this.center,
     this.right,
     this.backgroundColor
   }) : super(key: key);
 
-  UINode left;
-  UINode center;
-  List<UINode> right;
-  Color backgroundColor;
+  final UINode left;
+  final UINode center;
+  final List<UINode> right;
+  final Color backgroundColor;
 
   UINode build() {
     List<UINode> children = [
       left,
       new FlexExpandingChild(
         new Padding(
           child: center,
           padding: new EdgeDims.only(left: 24.0)
         ))
     ];
 
     if (right != null)
       children.addAll(right);
 
     return new Container(
       child: new FlexContainer(
         children: children,
         direction: FlexDirection.horizontal
       ),
       height: 56.0,
       padding: new EdgeDims(kStatusBarHeight.toDouble(), 8.0, 0.0, 8.0),
       decoration: new BoxDecoration(
         backgroundColor: backgroundColor,
         boxShadow: Shadow[2]
       )
     );
   }
 
 }