Prevent session invalidation behind c9.io proxies for concrete5.7

Session.php

<?php
/************
concrete/src/Session/Session.php
session validation starts at line 52 end at line 69 
comment out $session->invalidate();
behind c9 proxies we know the ip and agent change each request
leave comment for c9.io development only
*************/
namespace Concrete\Core\Session;

use Concrete\Core\Session\Storage\Handler\NativeFileSessionHandler;
use Concrete\Core\Utility\IPAddress;
use Config;
use \Symfony\Component\HttpFoundation\Session\Session as SymfonySession;
use \Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage;
use \Symfony\Component\HttpFoundation\Session\Storage\MockArraySessionStorage;
use Symfony\Component\HttpFoundation\Session\Storage\Handler\PdoSessionHandler;
use Core;

class Session
{

    public static function start()
    {
        $app = Core::make('app');
        if ($app->isRunThroughCommandLineInterface()) {
            $storage = new MockArraySessionStorage();
        } else {
            if (Config::get('concrete.session.handler') == 'database') {
                $db = \Database::get();
                $storage = new NativeSessionStorage(array(),
                    new PdoSessionHandler($db->getWrappedConnection(), array(
                            'db_table' => 'Sessions',
                            'db_id_col' => 'sessionID',
                            'db_data_col' => 'sessionValue',
                            'db_time_col' => 'sessionTime'
                        )
                    )
                );
            } else {
                $savePath = Config::get('concrete.session.save_path') ?: null;
                $storage = new NativeSessionStorage(array(), new NativeFileSessionHandler($savePath));
            }
            $options = Config::get('concrete.session.cookie');
            if ($options['cookie_path'] === false) {
                $options['cookie_path'] = $app['app_relative_path'] . '/';
            }
            $options['gc_max_lifetime'] = Config::get('concrete.session.max_lifetime');
            $storage->setOptions($options);
        }

        $session = new SymfonySession($storage);
        $session->setName(Config::get('concrete.session.name'));

        static::testSessionFixation($session);
        return $session;
    }

    protected static function testSessionFixation(SymfonySession $session)
    {
        $iph = Core::make('helper/validation/ip');
        $currentIp = $iph->getRequestIP();
        $ip = $session->get('CLIENT_REMOTE_ADDR');
        $agent = $session->get('CLIENT_HTTP_USER_AGENT');
        if ($ip && $ip != $currentIp->getIp(IPAddress::FORMAT_IP_STRING) || $agent && $agent != $_SERVER['HTTP_USER_AGENT']) {
            //c9.io development session fix
            //$session->invalidate();
        }
        if (!$ip && $currentIp !== false) {
            $session->set('CLIENT_REMOTE_ADDR', $currentIp->getIp(IPAddress::FORMAT_IP_STRING));
        }
        if (!$agent && isset($_SERVER['HTTP_USER_AGENT'])) {
            $session->set('CLIENT_HTTP_USER_AGENT', $_SERVER['HTTP_USER_AGENT']);
        }
    }
}

I'm guessing one of the c7 updates rewrote the session area, because I'm not seeing what you saying to comment out in any of the files. How can this be fixed today?

Solved using config please see:
https://www.concrete5.org/community/forums/installation/concrete5-on-cloud9

/application/config/concrete.php

<?php
// Get remote address
$remoteIp = $_SERVER['REMOTE_ADDR'];
return array(
    'security' => array(
        'trusted_proxies' => array(
            'ips' => [$remoteIp],
        ),
    ),
);