Remove the pointless second argument to animate() in AnimatedValue.

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 '../animation/animated_value.dart';
 import '../animation/curves.dart';
 import 'animated_component.dart';
 import 'basic.dart';
 
 typedef void ValueChanged(value);
 
 const double _kCheckDuration = 200.0;
 
 abstract class Toggleable extends AnimatedComponent {
 
   Toggleable({
     String key,
     this.value,
     this.onChanged
   }) : super(key: key) {
     toggleAnimation = new AnimatedValue(value ? 1.0 : 0.0);
+    watch(toggleAnimation);
   }
 
   bool value;
   AnimatedValue toggleAnimation;
   ValueChanged onChanged;
 
   void syncFields(Toggleable source) {
     onChanged = source.onChanged;
     if (value != source.value) {
       value = source.value;
@@ skipping 31 matching lines @@
         height: size.height,
         child: new CustomPaint(
           token: toggleAnimation.value,
           callback: customPaintCallback
         )
       ),
       onGestureTap: _handleClick
     );
   }
 }