Refactoring to support dark theme better

sky/sdk/lib/widgets/menu_item.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 '../painting/text_style.dart';
 import 'basic.dart';
 import 'button_base.dart';
 import 'default_text_style.dart';
 import 'icon.dart';
 import 'ink_well.dart';
@@ skipping 25 matching lines @@
   void syncFields(MenuItem source) {
     icon = source.icon;
     children = source.children;
     onPressed = source.onPressed;
     super.syncFields(source);
   }
 
   TextStyle get textStyle {
     TextStyle result = Theme.of(this).text.body2;
     if (highlight)
-      result = result.copyWith(color: Theme.of(this).primary[500]);
+      result = result.copyWith(color: Theme.of(this).primaryColor);
     return result;
   }
 
   Widget buildContent() {
     return new Listener(
       onGestureTap: (_) {
         if (onPressed != null)
           onPressed();
       },
       child: new Container(
@@ skipping 13 matching lines @@
                   child: new Flex(children, direction: FlexDirection.horizontal)
                 )
               )
             )
           ])
         )
       )
     );
   }
 }