How to detect the dragleave event in Firefox when dragging outside the window

Firefox doesn't properly trigger the dragleave event when dragging outside of the window:

https://bugzilla.mozilla.org/show_bug.cgi?id=665704

https://bugzilla.mozilla.org/show_bug.cgi?id=656164

I'm trying to develop a workaround for this (which I know is possible because Gmail is doing it), but the only thing I can come up with seems really hackish.

One way of knowing when dragging outside the window has occurred it to wait for the dragover event to stop firing (because dragover fires constantly during a drag and drop operation). Here's how I'm doing that:

var timeout;

function dragleaveFunctionality() {
  // do stuff
}

function firefoxTimeoutHack() {
  clearTimeout(timeout);
  timeout = setTimeout(dragleaveFunctionality, 200);
}

$(document).on('dragover', firefoxTimeoutHack);

This code is essentially creating and clearing a timeout over and over again. The 200 millisecond timeout will not be reached unless the dragover event stops firing.

While this works, I don't like the idea of using a timeout for this purpose. It feels wrong. It also means there's a slight lag before the "dropzone" styling goes away.

The other idea I had was to detect when the mouse leaves the window, but the normal ways of doing that don't seem to work during drag and drop operations.

Does anyone out there have a better way of doing this?

UPDATE:

Here's the code I am using:

 $(function() {
          var counter = 0;
          $(document).on('dragenter', f