getDocumentScrollElement()

gistfile1.js

(function() {
	document.addEventListener("DOMContentLoaded", function() {
		var elm = document.createElement('div');
		elm.setAttribute("style", "height:" + (window.innerHeight + 1) + "px;width:1px");
		document.body.appendChild(elm);
		document.body.scrollTop = 1;
		window.scrollElement = document.body.scrollTop > 1 ? document.body : document.documentElement;
		window.scrollElement.scrollTop -= 1;
		document.body.removeChild(blockElm);
	});
}());