Change the name of Component.render to Component.build in Effen

sky/examples/fn/widgets/button.dart

 part of widgets;
 
 class Button extends ButtonBase {
 
   static Style _style = new Style('''
     transform: translateX(0);
     display: inline-flex;
     border-radius: 4px;
     justify-content: center;
     align-items: center;
@@ skipping 11 matching lines @@
     border: 1px solid blue;
     -webkit-user-select: none;
     margin: 5px;
     background-color: orange;'''
   );
 
   Node content;
 
   Button({ Object key, this.content }) : super(key: key);
 
-  Node render() {
+  Node build() {
     return new Container(
       key: 'Button',
       style: _highlight ? _highlightStyle : _style,
-      children: [super.render(), content]
+      children: [super.build(), content]
     );
   }
 }