Allow Effen Styles to be extendable

sky/framework/components/drawer.dart

Index: sky/framework/components/drawer.dart
diff --git a/sky/framework/components/drawer.dart b/sky/framework/components/drawer.dart
index 6c792ccc283b7c142ac532b5b1e3b02022e91983..e2cfc99a9952a0d8fea9568f5a929649397346f7 100644
--- a/sky/framework/components/drawer.dart
+++ b/sky/framework/components/drawer.dart
@@ -150,21 +150,21 @@ class Drawer extends Component {
 
     Container mask = new Container(
       key: 'Mask',
-      styles: [_maskStyle],
+      style: _maskStyle,
       inlineStyle: maskInlineStyle
     )..events.listen('gesturetap', animation.handleMaskTap)
      ..events.listen('gestureflingstart', animation.handleFlingStart);
 
     Material content = new Material(
       key: 'Content',
-      styles: [_contentStyle],
+      style: _contentStyle,
       inlineStyle: contentInlineStyle,
       children: children,
       level: level
     );
 
     return new Container(
-      styles: [_style],
+      style: _style,
       inlineStyle: inlineStyle,
       children: [ mask, content ]
     );