Allow Effen Styles to be extendable

sky/framework/components/floating_action_button.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 '../fn.dart';
 import 'material.dart';
 import '../theme/colors.dart';
 
 class FloatingActionButton extends Component {
   static final Style _style = new Style('''
@@ skipping 25 matching lines @@
 
   FloatingActionButton({ Object key, this.content, this.level: 0 })
       : super(key: key);
 
   Node build() {
     List<Node> children = [];
 
     if (content != null)
       children.add(content);
 
-    List<Style> containerStyle = [_style];
-    if (level > 0)
-      containerStyle.add(Material.shadowStyle[level]);
-
     return new Container(
       key: "Container",
-      styles: containerStyle,
+      style: level > 0 ? _style.extend(Material.shadowStyle[level]) : _style,
       children: [
         new Material(
           key: "Clip",
-          styles: [_clipStyle],
+          style: _clipStyle,
           children: children
         )
       ]
     );
   }
 }