Make stocksapp.dart almost pass the dart analyzer.

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 15 matching lines @@
 
     return new Container(
       style: _style,
       children: children,
       key: _splashesKey
     )..events.listen('gesturescrollstart', _cancelSplashes)
      ..events.listen('wheel', _cancelSplashes)
      ..events.listen('pointerdown', _startSplash);
   }
 
-  sky.ClientRect _getBoundingRect() => getRoot().getBoundingClientRect();
+  sky.ClientRect _getBoundingRect() => (getRoot() as sky.Element).getBoundingClientRect();
 
-  void _startSplash(sky.Event event) {
+  void _startSplash(sky.PointerEvent event) {
     setState(() {
       if (_splashes == null) {
         _splashes = new LinkedHashSet<SplashAnimation>();
       }
 
       var splash;
       splash = new SplashAnimation(_getBoundingRect(), event.x, event.y,
                                    onDone: () { _splashDone(splash); });
 
       _splashes.add(splash);
@@ skipping 22 matching lines @@
     }
 
     setState(() {
       _splashes.remove(splash);
       if (_splashes.length == 0) {
         _splashes = null;
       }
     });
   }
 }