Allow Effen Styles to be extendable

sky/framework/components/fixed_height_scrollable.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 '../animation/scroll_behavior.dart';
 import '../fn.dart';
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'scrollable.dart';
 
@@ skipping 56 matching lines @@
 
         double drawStart = scrollOffset + alignmentDelta;
         itemNumber = (drawStart / _itemHeight).floor();
 
         transformStyle =
             'transform: translateY(${(alignmentDelta).toStringAsFixed(2)}px)';
       }
     }
 
     return new Container(
-      styles: [_style],
+      style: _style,
       children: [
         new Container(
-          styles: [_scrollAreaStyle],
+          style: _scrollAreaStyle,
           inlineStyle: transformStyle,
           children: buildItems(itemNumber, drawCount)
         )
       ]
     );
   }
 }