MenuActiveTrail::doGetActiveTrailIds

protected MenuActiveTrail::doGetActiveTrailIds($menu_name)

protected function doGetActiveTrailIds($menu_name) {
  // Parent ids; used both as key and value to ensure uniqueness.
  // We always want all the top-level links with parent == ''.
  $active_trail = array('' => '');

  // If a link in the given menu indeed matches the route, then use it to
  // complete the active trail.
  if ($active_link = $this->getActiveLink($menu_name)) {
    if ($parents = $this->menuLinkManager->getParentIds($active_link->getPluginId())) {
      $active_trail = $parents + $active_trail;
    }
  }

  return $active_trail;
}