Re-work MaterialComponent

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';
 import '../theme/shadows.dart';
 
-class FloatingActionButton extends Material {
+class FloatingActionButton extends Component {
   static final Style _style = new Style('''
     position: absolute;
     bottom: 16px;
     right: 16px;
     z-index: 5;
     transform: translateX(0);
     width: 56px;
     height: 56px;
     background-color: ${Red[500]};
     color: white;
@@ skipping 10 matching lines @@
     left: 0;
     right: 0;
     bottom: 0;
     -webkit-clip-path: circle(28px at center);''');
 
   Node content;
 
   FloatingActionButton({ Object key, this.content }) : super(key: key);
 
   Node build() {
-    List<Node> children = [super.build()];
+    List<Node> children = [];
 
     if (content != null)
       children.add(content);
 
     return new Container(
       key: "Container",
       style: _style,
       children: [
-        new Container(
+        new Material(
           key: "Clip",
           style: _clipStyle,
           children: children
         )
       ]
     );
   }
 }