modules/system/views_handler_argument_file_fid.inc

<?php
class views_handler_argument_file_fid extends views_handler_argument_numeric {
  function title_query() {
    $titles = db_select('file_managed', 'f')
      ->fields('f', array('filename'))
      ->condition('fid', $this->value)
      ->execute()
      ->fetchCol();
    foreach ($titles as &$title) {
      $title = check_plain($title);
    }
    return $titles;
  }
}