code: function reportMessages(isPolite, types) {
      var politeness = isPolite ? 'polite' : 'assertive';
      var messages = [];
  
      if (types & ReportType.Selected && ctrl.index !== -1) {
        messages.push(getCurrentDisplayValue());
      }
  
      if (types & ReportType.Count) {
        messages.push($q.resolve(getCountMessage()));
      }
  
      $q.all(messages).then(function(data) {
        $mdLiveAnnouncer.announce(data.join(' '), politeness);
      });
    }
docs: Reports given message types to supported screen readers.
  @param {boolean} isPolite Whether the announcement should be polite.
  @param {!number} types Message flags to be reported to the screen reader.