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

vendor/symfony/http-foundation/Session/Flash/FlashBagInterface.php

@@ -0,0 +1,93 @@
+<?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\Flash;
+
+use Symfony\Component\HttpFoundation\Session\SessionBagInterface;
+
+/**
+ * FlashBagInterface.
+ *
+ * @author Drak <drak@zikula.org>
+ */
+interface FlashBagInterface extends SessionBagInterface
+{
+    /**
+     * Adds a flash message for type.
+     *
+     * @param string $type
+     * @param string $message
+     */
+    public function add($type, $message);
+
+    /**
+     * Registers a message for a given type.
+     *
+     * @param string       $type
+     * @param string|array $message
+     */
+    public function set($type, $message);
+
+    /**
+     * Gets flash messages for a given type.
+     *
+     * @param string $type    Message category type.
+     * @param array  $default Default value if $type does not exist.
+     *
+     * @return array
+     */
+    public function peek($type, array $default = array());
+
+    /**
+     * Gets all flash messages.
+     *
+     * @return array
+     */
+    public function peekAll();
+
+    /**
+     * Gets and clears flash from the stack.
+     *
+     * @param string $type
+     * @param array  $default Default value if $type does not exist.
+     *
+     * @return array
+     */
+    public function get($type, array $default = array());
+
+    /**
+     * Gets and clears flashes from the stack.
+     *
+     * @return array
+     */
+    public function all();
+
+    /**
+     * Sets all flash messages.
+     */
+    public function setAll(array $messages);
+
+    /**
+     * Has flash messages for a given type?
+     *
+     * @param string $type
+     *
+     * @return bool
+     */
+    public function has($type);
+
+    /**
+     * Returns a list of all defined types.
+     *
+     * @return array
+     */
+    public function keys();
+}