s.listen(goog.dom.getElement('enable_doc'),
        goog.events.EventType.CLICK,
        function(e) {
          hc.getChild('Doc').setEnabled(e.target.checked);
        });
    goog.events.listen(goog.dom.getElement('enable_hc_events'),
        goog.events.EventType.CLICK,
        function(e) {
          hc.forEachChild(function(c) {
            if (e.target.checked) {
              // Enable all transition events.
              c.setDispatchTransitionEvents(goog.ui.Component.State.ALL, true);
            