The current scroll behavior of this widget.
Scroll behaviors control where the boundaries of the scrollable are placed and how the scrolling physics should behave near those boundaries and after the user stops directly manipulating the scrollable.
Source
@override
ExtentScrollBehavior get scrollBehavior {
if (config.itemsWrap) {
_unboundedBehavior ??= new UnboundedBehavior(platform: platform);
return _unboundedBehavior;
}
_overscrollBehavior ??= new OverscrollBehavior(platform: platform);
return _overscrollBehavior;
}