Bug 131676 – 'mousewheel'-event is not fired inside an iFrame under certain conditions

• Status: NEW
• Component: UI Events

Preconditions:
A webpage living inside an iFrame contains a <script>-tag in which another script-element is programmatically created and its src-property is set to an external JavaScript-file:

<script>
    var elem = document.createElement("script");
    var head = document.getElementsByTagName("head")[0];
    head.appendChild(elem);
    elem.src = "externalScript.js";
</script> 

Bug:
The setting of the script-element's src-property brakes the firing of mousewheel-events inside the iFrame (see attached example, where no 'mouse wheel' logs will appear in the console.)
 
Workaround:
If you put the statement

  window.onmousewheel = function(){};

inside of a script-tag (not in an external JS-file!), then the webpage inside the iFrame reacts to mousewheel-events again.


Please find a reduced example demonstrating this bug and the found workaround attached.