How to fire mouse wheel event in Firefox with JavaScript?

I'm trying to do automated testing with WebDriver, but it currently has no ability to simulate mouse wheel events. As a workaround I'm trying to fire these events with JavaScript instead. I'm doing all my wheel experimenting on a straight HTML page right now, not within the WebDriver framework.

I'm specifically trying to fire a mouse wheel event on a scrolling div element.

So far I've been able to do this with Chrome and IE9, but I can't seem to get anything to work in Firefox (5.x).

I'm using the following cross-browser code to detect when mouse wheel events are fired, which I snagged off the net. This code is able to pick up the event in all browsers when I scroll the mouse wheel within the scrolling div I've created (id='view').

<script type="text/javascript">
  function wheel(event) {
    var delta = 0;
    if (!event) {
      event = view.event;
    }
    if (event.wheelDelta) {
      delta = event.wheelDelta / 120;
    }
    else if (event.detail) {
      delta = -event.detail / 3;
    }
    
    alert(delta);
  }
  
  var view = document.getElementById('view');
  
  if (view.addEventListener) {
    view.addEventListener('DOMMouseScroll', wheel, false);
  }
  
  view.onmousewheel = wheel;
</script>

The function below, when called, is able fire the mouse wheel event in Chrome and IE9, and gets picked up in the above handler with expected behavior.

function ChromeWheel () {
  var evt = document.createEvent("MouseEvents");
  evt.initEvent('mousewheel', true, true);
  evt.wheelDelta = 120;
  view.dispatchEvent(evt);
}

Of course, it does not work for Firefox. I've found existing documentation to be too sparse and confusing to know how FF handles this. Can anyone show me the bare minimum to fire a mouse wheel event in Firefox with a wheel delta (placed where Firefox expects it), such that my handler will pick it up?