>Why do you call this FIREFOX?

Sorry, this is a cut and paste error. I just "borrowed" the code from https://github.com/mozilla/pdf.js/blob/master/web/viewer.js#L3200. (BTW: doesn't this mean that scrolling in fullscreen mode is "broken" in other browsers.)
Of course this won't work in other browsers, since `DOMMouseScroll` is Firefox specific. I'm going to look into making this platform independent. Thanks!