Rationalize Dart mojo and sky package structure

sky/sdk/lib/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 'curves.dart';
 import 'dart:async';
 import 'generators.dart';
 
 typedef void Callback ();
 
@@ skipping 62 matching lines @@
     return _completer.future;
   }
 
   double get remainingTime {
     if (_animation == null)
       return 0.0;
     return _animation.remainingTime;
   }
 
 }