anchor.diff:        return config._buildIndicator(context, 0.0, 0.0, 0, 0.0);
   
       return new AnimatedBuilder(
  -      animation: _animation,
  +      animation: _animationController,
         builder: (BuildContext context, Widget child) {
           return config._buildIndicator(context,
  -            _kStrokeHeadTween.evaluate(_animation),
  -            _kStrokeTailTween.evaluate(_animation),
  -            _kStepTween.evaluate(_animation),
  -            _kRotationTween.evaluate(_animation));
  +            _kStrokeHeadTween.evaluate(_animationController),
  +            _kStrokeTailTween.evaluate(_animationController),
  +            _kStepTween.evaluate(_animationController),
  +            _kRotationTween.evaluate(_animationController));
         }
       );
     }
  
positive.code:   void paint(Canvas canvas, Size size) {
      Paint paint = new Paint()
        ..color = backgroundColor
        ..style = ui.PaintingStyle.fill;
      canvas.drawRect(Point.origin & size, paint);
  
      paint.color = valueColor;
  
negative.code: 
  // TODO(jestelle) This should probably go somewhere else?  And maybe be more
  // general?  Or maybe the IntTween should actually work this way?
  class _StepTween extends Tween<int> {
    _StepTween({ int begin, int end }) : super(begin: begin, end: end);
  
    // The inherited lerp() function doesn't work with ints because it multiplies
    // the begin and end types by a double, and int * double returns a double.
  