Fix bugs of pending keys of animated menu. - When more than one pending key, the animation would be stoped. - Now, we have a cyclic queue to keep at most 15 pending keys to make sure pending keys being dispatched without stop current animation program.

function start_madbuilder() {
    var url = "chrome://MadBuilder/content/madbuilder.html";
    var browser = document.getElementById("content");

    browser.loadURI(url, null, null, true);
}