Rename UINode to Widget.

sky/sdk/lib/widgets/scrollable.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:math' as math;
 import 'dart:sky' as sky;
 
 import '../framework/animation/generators.dart';
 import '../framework/animation/mechanics.dart';
 import '../framework/animation/scroll_behavior.dart';
@@ skipping 30 matching lines @@
   ScrollBehavior _scrollBehavior;
   ScrollBehavior createScrollBehavior();
   ScrollBehavior get scrollBehavior {
     if (_scrollBehavior == null)
       _scrollBehavior = createScrollBehavior();
     return _scrollBehavior;
   }
 
   Simulation _simulation;
 
-  UINode buildContent();
+  Widget buildContent();
 
-  UINode build() {
+  Widget build() {
     return new EventListenerNode(
       new Material(
         child: buildContent(),
         edge: MaterialEdge.canvas,
         color: backgroundColor
       ),
       onPointerDown: _handlePointerDown,
       onPointerUp: _handlePointerUpOrCancel,
       onPointerCancel: _handlePointerUpOrCancel,
       onGestureFlingStart: _handleFlingStart,
@@ skipping 91 matching lines @@
 
   void _handleFlingCancel(sky.GestureEvent event) {
     _startSimulation(_createParticle());
   }
 
   void _handleWheel(sky.WheelEvent event) {
     scrollBy(-event.offsetY);
   }
 
 }