if (!window.addEventListener) {
    window.addEventListener = add_event_listener;
}

function add_event_listener(type, listener, useCapture) {
    // useCapture does nothing here.
    var oldEventListener = window['on' + type] ? window['on' + type] : function() {void 0;};
    window['on' + type] = function() { oldEventListener(); listener(); };
}