Programatic scroll edge effect for NSScrollView

Just like NSScrollView lets us programmatically set the contentInset in parallel to automaticallyAdjustsContentInsets, I think there should be similar functionality for blurring effect caused by scroll edge effect. I should be able programmatically set it.

If the user is manually setting the contentInset then they can simply set a boolean, which when enabled will show edge effect when the scroll document goes outside the area of inset.

Eg:

scrollView.contentInsets = NSEdgeInsets(top: 100, left: 0, bottom: 0, right: 0)

For contentInset like above set by user, they could set edge effect in two ways

1. Automatically:

scrollView.enableEdgeEffectOutsideInsets = true 
// This will apply edge effect based on frame size of contentInsets

1. Programmatically:

scrollView.edgeInsetEffectFrame = NSRect...