Rationalize Dart mojo and sky package structure

sky/sdk/lib/framework/animation/fling_curve.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;
 
 const double _kDefaultAlpha = -5707.62;
 const double _kDefaultBeta = 172.0;
 const double _kDefaultGamma = 3.7;
 
@@ skipping 35 matching lines @@
   double update(double timeStamp) {
     double t = timeStamp / 1000.0 - _startTime + _timeOffset;
     if (t >= _kCurveDuration)
       return 0.0;
     double position = _positionAtTime(t) - _positionOffset;
     double positionDelta = position - _previousPosition;
     _previousPosition = position;
     return _direction * math.max(0.0, positionDelta);
   }
 }