Rename UINode to Widget.

sky/sdk/lib/widgets/toggleable.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:sky' as sky;
 
 import 'animated_component.dart';
 import 'basic.dart';
 import '../framework/animation/animated_value.dart';
 import '../framework/animation/curves.dart';
@@ skipping 39 matching lines @@
   // Override these methods to draw yourself
   void customPaintCallback(sky.Canvas canvas, Size size) {
     assert(false);
   }
   Size get size => Size.zero;
   EdgeDims get margin => const EdgeDims.symmetric(horizontal: 5.0);
   double get duration => 200.0;
   Curve get curveUp => easeIn;
   Curve get curveDown => easeOut;
 
-  UINode build() {
+  Widget build() {
     return new EventListenerNode(
       new Container(
         margin: margin,
         width: size.width,
         height: size.height,
         child: new CustomPaint(
           token: toggleAnimation.value,
           callback: customPaintCallback
         )
       ),
       onGestureTap: _handleClick
     );
   }
 }