Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/symfony/http-foundation/Session/SessionBagInterface.php

@@ -0,0 +1,48 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\HttpFoundation\Session;
+
+/**
+ * Session Bag store.
+ *
+ * @author Drak <drak@zikula.org>
+ */
+interface SessionBagInterface
+{
+    /**
+     * Gets this bag's name.
+     *
+     * @return string
+     */
+    public function getName();
+
+    /**
+     * Initializes the Bag.
+     *
+     * @param array $array
+     */
+    public function initialize(array &$array);
+
+    /**
+     * Gets the storage key for this bag.
+     *
+     * @return string
+     */
+    public function getStorageKey();
+
+    /**
+     * Clears out data from bag.
+     *
+     * @return mixed Whatever data was contained.
+     */
+    public function clear();
+}