function selectItemOnMatch () {
    var searchText = $scope.searchText,
        matches    = ctrl.matches,
        item       = matches[ 0 ];
    if (matches.length === 1) getDisplayValue(item).then(function (displayValue) {
      var isMatching = searchText === displayValue;
      if ($scope.matchInsensitive && !isMatching) {
        isMatching = searchText.toLowerCase() === displayValue.toLowerCase();
      }

      if (isMatching) {
        select(0);
      }
    });
  }
If there is only one matching item and the search text matches its display value exactly,
automatically select that item.  Note: This function is only called if the user uses the
`md-select-on-match` flag.