[Effen] Tapping on a menu while it's closing should not make it instantly disappear.

sky/framework/animation/animated_value.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 '../fn.dart';
 import 'curves.dart';
 import 'dart:async';
 import 'generators.dart';
 
 class AnimatedValue {
@@ skipping 29 matching lines @@
     _animation = null;
     if (_completer == null)
       return;
     Completer completer = _completer;
     _completer = null;
     completer.complete(_value);
   }
 
   void stop() {
     if (_animation != null) {
-      _animation.cancel();
+      _animation.cancel(); // will call _done() if it isn't already finished
       _done();
     }
   }
 
   Future<double> animateTo(double newValue, double duration,
       { Curve curve: linear, double initialDelay: 0.0 }) {
     stop();
 
     _animation = new AnimationGenerator(
         duration: duration,
         begin: _value,
         end: newValue,
         curve: curve,
         initialDelay: initialDelay)
       ..onTick.listen(_setValue, onDone: _done);
 
     _completer = new Completer();
     return _completer.future;
   }
 
   double get remainingTime {
     if (_animation == null)
       return 0.0;
     return _animation.remainingTime;
   }
 
 }