Make isBorderBox padding modification apply only to input elements

The border box modification to padding applies only for input elements. Rendering of textarea elements is broken by this fix: http://jsfiddle.net/f2ec8/1/

This is a fixed version with this commit applied: http://jsfiddle.net/FbYLf/1/
Yeah—it could be

    var isNotTextarea = !$this.is('textarea');

or even

    var isNotTextarea = $this.is(':not(textarea)');

Would that be preferable?