_toolbar_do_get_rendered_subtrees

_toolbar_do_get_rendered_subtrees(array $data)

function _toolbar_do_get_rendered_subtrees(array $data) {
  $menu_tree = \Drupal::service('toolbar.menu_tree');
  // Load the administration menu. The first level is the "Administration" link.
  // In order to load the children of that link and the subsequent two levels,
  // start at the second level and end at the fourth.
  $parameters = new MenuTreeParameters();
  $parameters->setMinDepth(2)->setMaxDepth(4)->onlyEnabledLinks();
  // @todo Make the menu configurable in https://www.drupal.org/node/1869638.
  $tree = $menu_tree->load('admin', $parameters);
  $manipulators = array(
    array('callable' => 'menu.default_tree_manipulators:checkAccess'),
    array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
    array('callable' => 'toolbar_menu_navigation_links'),
  );
  $tree = $menu_tree->transform($tree, $manipulators);
  $subtrees = array();
  // Calculated the combined cacheability of all subtrees.
  $cacheability = new CacheableMetadata();
  foreach ($tree as $element) {
    /** @var \Drupal\Core\Menu\MenuLinkInterface $link */
    $link = $element->link;
    if ($element->subtree) {
      $subtree = $menu_tree->build($element->subtree);
      $output = \Drupal::service('renderer')->renderPlain($subtree);
      $cacheability = $cacheability->merge(CacheableMetadata::createFromRenderArray($subtree));
    }
    else {
      $output = '';
    }
    // Many routes have dots as route name, while some special ones like <front>
    // have <> characters in them.
    $url = $link->getUrlObject();
    $id = str_replace(array('.', '<', '>'), array('-', '', ''), $url->isRouted() ? $url->getRouteName() : $url->getUri());

    $subtrees[$id] = $output;
  }

  // Store the subtrees, along with the cacheability metadata.
  $cacheability->applyTo($data);
  $data['#subtrees'] = $subtrees;

  return $data;
}