customizeSegment method
Changes the series color, border color and border width.
Implementation
@override
void customizeSegment(ChartSegment segment) {
final StepAreaSegment<T, D> stepAreaSegment =
segment as StepAreaSegment<T, D>;
updateSegmentColor(stepAreaSegment, borderColor, borderWidth);
updateSegmentGradient(stepAreaSegment,
gradientBounds: stepAreaSegment._fillPath.getBounds(),
gradient: gradient,
borderGradient: borderGradient);
}