modules/aggregator/views_handler_argument_aggregator_fid.inc

<?php

class views_handler_argument_aggregator_fid extends views_handler_argument_numeric {
  function title_query() {
    $titles = array();

    $result = db_query("SELECT f.title FROM {aggregator_feed} f WHERE f.fid IN (:fids)", array(':fids' => $this->value));
    foreach ($result as $term) {
      $titles[] = check_plain($term->title);
    }
    return $titles;
  }
}