see $_GET['lang'] = $this->getLangKey(); above.. the reason it has to go into the "get" is because we do a mock request for resource loader. 

It would be cleaner to have have a "mock" request object so that it does not look as dangerous. ... also to make people feel better about the key... we should use    $this->getCustomSkinKey() and $this->getLangKey() as we build out that cache key.