anchor.diff:      int divisions,
       String label,
       Color activeColor,
  +    TextTheme textTheme,
       this.onChanged,
       TickerProvider vsync,
     }) : _value = value,
          _divisions = divisions,
          _activeColor = activeColor,
  +       _textTheme = textTheme,
           super(additionalConstraints: _getAdditionalConstraints(label)) {
       assert(value != null && value >= 0.0 && value <= 1.0);
       this.label = label;
  
positive.code:     if (value == _activeColor)
        return;
      _activeColor = value;
      markNeedsPaint();
    }
  
  
negative.code:       // https://github.com/flutter/flutter/issues/5938
        _labelPainter
          ..text = new TextSpan(
            style: _textTheme.body1.copyWith(fontSize: 10.0),
            text: newLabel
          )
          ..layout();
  