Allow Effen Styles to be extendable

sky/framework/components/material.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 '../theme/shadows.dart';
 import 'dart:collection';
 import 'dart:sky' as sky;
 import 'ink_splash.dart';
 
@@ skipping 11 matching lines @@
     null,
     new Style('box-shadow: ${Shadow[1]}'),
     new Style('box-shadow: ${Shadow[2]}'),
     new Style('box-shadow: ${Shadow[3]}'),
     new Style('box-shadow: ${Shadow[4]}'),
     new Style('box-shadow: ${Shadow[5]}'),
   ];
 
   LinkedHashSet<SplashAnimation> _splashes;
 
-  List<Style> styles;
+  Style style;
   String inlineStyle;
   List<Node> children;
   int level;
 
   Material({
       Object key,
-      this.styles,
+      this.style,
       this.inlineStyle,
       this.children,
       this.level: 0 }) : super(key: key) {
     events.listen('gesturescrollstart', _cancelSplashes);
     events.listen('wheel', _cancelSplashes);
     events.listen('pointerdown', _startSplash);
   }
 
   Node build() {
     List<Node> childrenIncludingSplashes = [];
 
     if (_splashes != null) {
       childrenIncludingSplashes.add(new Container(
-        styles: [_splashesStyle],
+        style: _splashesStyle,
         children: new List.from(_splashes.map(
             (s) => new InkSplash(s.onStyleChanged))),
         key: 'Splashes'
       ));
     }
 
     if (children != null)
       childrenIncludingSplashes.addAll(children);
 
-    List<Style> stylesIncludingShadow = styles;
-    if (level > 0) {
-      stylesIncludingShadow = new List.from(styles);
-      stylesIncludingShadow.add(shadowStyle[level]);
-    }
-
-    return new Container(key: 'Material', styles: stylesIncludingShadow,
-        inlineStyle: inlineStyle, children: childrenIncludingSplashes);
+    return new Container(
+        key: 'Material',
+        style: level > 0 ? style.extend(shadowStyle[level]) : style,
+        inlineStyle: inlineStyle,
+        children: childrenIncludingSplashes
+    );
   }
 
   sky.ClientRect _getBoundingRect() => (getRoot() as sky.Element).getBoundingClientRect();
 
   void _startSplash(sky.PointerEvent event) {
     setState(() {
       if (_splashes == null) {
         _splashes = new LinkedHashSet<SplashAnimation>();
       }
 
@@ skipping 27 matching lines @@
     }
 
     setState(() {
       _splashes.remove(splash);
       if (_splashes.length == 0) {
         _splashes = null;
       }
     });
   }
 }