attempt at making menuitems react

sky/examples/fn/widgets/drawer.dart

 part of widgets;
 
 const double _kWidth = 256.0;
 const double _kMinFlingVelocity = 0.4;
 const double _kMinAnimationDurationMS = 246.0;
 const double _kMaxAnimationDurationMS = 600.0;
 const Cubic _kAnimationCurve = easeOut;
 
 class DrawerAnimation {
 
@@ skipping 102 matching lines @@
     top: 0;
     left: 0;
     bottom: 0;
     right: 0;'''
   );
 
   static Style _contentStyle = new Style('''
     background-color: #FAFAFA;
     will-change: transform;
     position: absolute;
+    z-index: 3;
     width: 256px;
     top: 0;
     left: 0;
     bottom: 0;'''
   );
 
   Stream<double> onPositionChanged;
   sky.EventListener handleMaskFling;
   sky.EventListener handleMaskTap;
   sky.EventListener handlePointerCancel;
@@ skipping 57 matching lines @@
         new Container(
           key: 'Content',
           style: _contentStyle,
           inlineStyle: contentInlineStyle,
           children: children
         )
       ]
     );
   }
 }