Steps to Reproduce

<calendar/>
1. include za11y.jar
2. focus on icons on the calendar header with the Tab key

Current Result

cannot achieve it

Expected Result

can focus on those icons with the Tab key

Debug Information

• za11y.wpd make the Calendar header non-focusable:

      bind_: function bind_() {
        ...
        [this.$n('left'), this.$n('title'), this.$n('right')].forEach(function (l) {
          if (l) {
            l.tabIndex = -1;
            l.setAttribute('aria-hidden', true);
          }
        });
  

• according to https://www.w3.org/WAI/ARIA/apg/patterns/combobox/examples/combobox-datepicker/, the icons to change the month is focusable