this little function determines the top scrolling element on the page on any device..

determineScrollingElement.js

function determineScrollingElement(callback) {
		
	var self = this;
	var div = $("<div style='height: 10000px;'></div>").appendTo(document.body);

	var interval = window.setInterval(function() {
		
		document.body.scrollTop = 50;
		document.documentElement.scrollTop = 100;
		
		if(window.pageYOffset != 0 || document.body.scrollTop != 0) { // finally, scrolling conditions are good if this attribute is non-zero

			clearInterval(interval);

			if(window.pageYOffset == 0) // this is likely a Palm Pre 2 or something like it
				self.pageOffsetNotSupported = true;

			if(document.body.scrollTop > 0)
				self.scrollingElement = document.body;
					
			if(document.documentElement.scrollTop > 0)
				self.scrollingElement = document.documentElement;
				
			if(!document.body.scrollTop && !document.documentElement.scrollTop)
				self.scrollingElement = document.body; // holy crap it's an iPhone...doesn't allow you to read scrollTop, but set

			document.body.scrollTop = 0;
			document.documentElement.scrollTop = 0;
			div.remove();
			callback.call(self);
			
		}
			
	}, 13);
		
}