Support for background images on cards, style demo home

sky/sdk/lib/widgets/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 '../painting/box_painter.dart';
 import '../theme/colors.dart' as colors;
 import '../theme/edges.dart';
 import '../theme/shadows.dart';
 import 'basic.dart';
 import 'default_text_style.dart';
 import 'theme.dart';
 
+export '../theme/edges.dart' show MaterialEdge;
+
 class Material extends Component {
 
   Material({
     String key,
     this.child,
     this.edge: MaterialEdge.card,
     this.level: 0,
     this.color
   }) : super(key: key);
 
@@ skipping 21 matching lines @@
         boxShadow: shadows[level],
         borderRadius: edges[edge],
         backgroundColor: backgroundColor,
         shape: edge == MaterialEdge.circle ? Shape.circle : Shape.rectangle
       ),
       child: new DefaultTextStyle(style: Theme.of(this).text.body1, child: child)
     );
   }
 
 }