Feature test for hidden scrollbars (e. g. on Mac OS). Adopted from http://davidwalsh.name/detect-scrollbar-width and https://github.com/Modernizr/Modernizr/blob/d6e1d6f09e1f8250eca9116bcffe2f846616afa7/feature-detects/hiddenscroll.js. Usage: Plug it in and see the class "hiddenscroll" being added to the html element if scrollbars are hidden.

jquery.hiddenscroll.js

(function ($) {
	$(function () {
		var el = $('<div style="width:100px;height:100px;overflow:scroll;position:absolute;top:-9999px;"/>'),
			elDom = el.get(0);
		el.appendTo("body");
		if (elDom.offsetWidth === elDom.clientWidth) {
			$("html").addClass("hiddenscroll");
		}
		el.remove();
	});
})(jQuery);

FYI: Internet Explorer Edge (IE12!) on Win10 dynamically sets the scrollbar width to zero when you go into Tablet Mode, and shows the scrollbar again when you leave Tablet Mode. I think you can detect the mode change by registering for a resize event.