[Effen] Reduce splashes when scrolling.

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 49 matching lines @@
         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;
+  }
+
 }