Allow Effen Styles to be extendable

sky/framework/components/floating_action_button.dart

Index: sky/framework/components/floating_action_button.dart
diff --git a/sky/framework/components/floating_action_button.dart b/sky/framework/components/floating_action_button.dart
index 1752710cdc3f4c2375119ee0aaeb648b9db2f455..93fd61b50be6bac37ffdefb962a14b22c0ea5278 100644
--- a/sky/framework/components/floating_action_button.dart
+++ b/sky/framework/components/floating_action_button.dart
@@ -43,17 +43,13 @@ class FloatingActionButton extends Component {
     if (content != null)
       children.add(content);
 
-    List<Style> containerStyle = [_style];
-    if (level > 0)
-      containerStyle.add(Material.shadowStyle[level]);
-
     return new Container(
       key: "Container",
-      styles: containerStyle,
+      style: level > 0 ? _style.extend(Material.shadowStyle[level]) : _style,
       children: [
         new Material(
           key: "Clip",
-          styles: [_clipStyle],
+          style: _clipStyle,
           children: children
         )
       ]