If keyboard is visible upon initial layout.

[markst]

Needs to check whether the keyboard is visible on creation & update the constant accordingly.

[markst]

Not sure what's appropriate for this. Since we should be checking whether keyboard is visible at time of view layout rather than creation of constraint.
i.e a keyboard might be visible a the time the constraint is created for vc, but when presented modally will dismiss the keyboard... which in fact wont be an issue.