This is sort of a ridiculous hack, but you could probably override Element.prototype.webkitRequestFullscreen, and manually resize the element to take up the whole browseer window rather than entering fullscreen.
At one point I did try this, but it ends up being a much more complex solution. It turns out it's fairly difficult to ensure the element appears above every other element. I was using 'position: fixed' with the maximum z-index value.
