Tooltip: doesn't position correctly when scrolled off page

First, I did search for an existing bug ticket. All I found was a commit from 2010 that sounds like it addresses the exact problem I'm having, but the code has since been changed: https://github.com/jquery/jquery-ui/commit/18a526ad78a0b154e6ce6dc430a025bec7fa2ee2

I've tested with jQuery UI 1.10.4 and 1.11.0-beta.2, both using jQuery 1.11.0.

The problem occurs with Firefox 24.1.0 (ESR), Chrome 34.0.1847.137 m, and IE 10 on Windows 7 Enterprise. I haven't tested any other browsers or operating systems.

To reproduce:

1. Add a tooltip to an element on a page.

2. Add an event handler to a button at the bottom of the page that opens the tooltip.

3. When the event handler is called, the tooltip should display below the element it is attached to (this is assuming the default position option).

4. Add a large margin-bottom to the button at the bottom of the page.

5. Scroll down so that you can see the button but not the element the tooltip is attached to.

6. When the event handler is called, the tooltip will display above the element it is attached to.

The tooltip should display below the element regardless of scrolling. The same thing occurs with any option other than the default position.

Here's a demo: http://jsfiddle.net/b9CKT/

I poked around in the jQuery UI files for about an hour and couldn't determine a solution. Sorry.