user_agent.php
public function restart($date = false)
    {
        $this->cookie_jar->restartSession($date);
        $this->authenticator->restartSession();
        $this->http_referer = null;
    }
public function restart($date = false)
    {
        $this->cookie_jar->restartSession($date);
        $this->authenticator->restartSession();
        $this->http_referer = null;
    }
Removes expired and temporary cookies as if the browser was closed and re-opened.
Authorisation has to be obtained again as well.

@param string/integer $date   Time when session restarted. If omitted then all persistent
cookies are kept.