code: function _doPopulate() {
          var dropdownItems = [Strings.NEW_FILE_FILTER, Strings.CLEAR_FILE_FILTER],
              filterSets = PreferencesManager.get("fileFilters") || [];
  
          if (filterSets.length) {
              dropdownItems.push("---");
  
              // Remove all the empty exclusion sets before concatenating to the dropdownItems.
              filterSets = filterSets.filter(function (filter) {
                  return (_getCondensedForm(filter.patterns) !== "");
              });
  
              // FIRST_FILTER_INDEX needs to stay in sync with the number of static items (plus separator)
              // ie. the number of items populated so far before we concatenate with the actual filter sets.
              dropdownItems = dropdownItems.concat(filterSets);
          }
          _picker.items = dropdownItems;
      }
docs: Populate the list of dropdown menu with two filter commands and
  the list of saved filter sets.