Effen: willUmount->didUnmount, allow setState after didUnmount

sky/examples/fn/widgets/material.dart

 part of widgets;
 
 abstract class MaterialComponent extends Component {
 
   static const _splashesKey = const Object();
 
   static Style _style = new Style('''
     transform: translateX(0);
     position: absolute;
     top: 0;
@@ skipping 43 matching lines @@
       return;
     }
 
     setState(() {
       var splashes = _splashes;
       _splashes = null;
       splashes.forEach((s) { s.cancel(); });
     });
   }
 
-  void willUnmount() {
+  void didUnmount() {
     _cancelSplashes(null);
   }
 
   void _splashDone(SplashAnimation splash) {
     if (_splashes == null) {
       return;
     }
 
     setState(() {
       _splashes.remove(splash);
       if (_splashes.length == 0) {
         _splashes = null;
       }
     });
   }
 }