/**
* {@inheritdoc}
*/
public function getCacheKeys()
{
// Add a key for the active menu trail.
$menu = $this->getDerivativeId();
$active_trail = $this->menuTree->getActiveTrailIds($menu);
$active_trail_key = 'trail.' . implode('|', $active_trail);
return array_merge(parent::getCacheKeys(), array($active_trail_key));
}
