modules/taxonomy/views_handler_argument_term_node_tid.inc

<?php
class views_handler_argument_term_node_tid extends views_handler_argument_many_to_one {
  function option_definition() {
    $options = parent::option_definition();
    $options['set_breadcrumb'] = array('default' => FALSE);
    return $options;
  }

  function options_form(&$form, &$form_state) {
    parent::options_form($form, $form_state);
    $form['set_breadcrumb'] = array(
      '#type' => 'checkbox',
      '#title' => t("Set the breadcrumb for the term parents"),
      '#description' => t('If selected, the breadcrumb trail will include all parent terms, each one linking to this view. Note that this only works if just one term was received.'),
      '#default_value' => !empty($this->options['set_breadcrumb']),
    );
  }

  function set_breadcrumb(&$breadcrumb) {
    if (empty($this->options['set_breadcrumb']) || !is_numeric($this->argument)) {
      return;
    }

    return views_taxonomy_set_breadcrumb($breadcrumb, $this);
  }

  function title_query() {
    $titles = array();
    $result = db_select('taxonomy_term_data', 'td')
      ->fields('td', array('name'))
      ->condition('td.tid', $this->value)
      ->execute();
    foreach ($result as $term) {
      $titles[] = check_plain($term->name);
    }
    return $titles;
  }
}