Extending JLinkedApiLibrary class to pass redirect url

class JLinkedApiLibraryX extends JLinkedApiLibrary
{
    // Override model's getInstance to really only get the instance
    protected $configModel;
    protected $memberId;
    protected $mappedFbUserId;
    protected $retryCount = 0;
    protected $timestampOffset = null;
    private static $libraryInstance;

    public static function getInstance($returl)
    {
        if (!isset(self::$libraryInstance))
        {
            self::$libraryInstance = new JLinkedApiLibraryX($returl);
            // After the instance is grabbed, get the Javascript code to insert
            // Don't do this in the constructor as inititing the Javascript calls functions which need
            //   this very instance
            $app = JFactory::getApplication();
            if (!$app->isAdmin())
            {
                // Set whether, on this page load, the user should be checked for a new mapping (i.e. they were just on the login/register page)
                $session = JFactory::getSession();
                $checkNewMapping = $session->get('jLinkedCheckNewMapping', false);
                self::$libraryInstance->checkNewMapping = $checkNewMapping;
            }
        }
        return self::$libraryInstance;
    }

    function __construct($returl)
    {
        $this->getConfigModel();
        $this->setTimestampOffset($this->configModel->getSetting('linkedin_oauth_timestamp_offset'));
        $this->findLocalAccessToken(); // Search for an access token and set it

        $return = ''; $menuItemId = 0;
        SCSocialUtilities::getCurrentReturnParameter($return, $menuItemId, LOGIN_TASK_JLINKED);

        $linkedInApiKey = $this->configModel->getSetting('linkedin_api_key');
        $linkedInSecretKey = $this->configModel->getSetting('linkedin_secret_key');
		$callbackUrl = $returl;
        if (!$callbackUrl) $callbackUrl = JURI::root() . 'index.php?option=com_jlinked&task=linkedInCallback&return='.base64_encode($return);
        $config = array('appKey' => $linkedInApiKey, 'appSecret' => $linkedInSecretKey, 'callbackUrl' => $callbackUrl);
        parent::__construct($config);
    }

}