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

vendor/symfony/browser-kit/History.php

@@ -0,0 +1,102 @@
+<?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\BrowserKit;
+
+/**
+ * History.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class History
+{
+    protected $stack = array();
+    protected $position = -1;
+
+    /**
+     * Clears the history.
+     */
+    public function clear()
+    {
+        $this->stack = array();
+        $this->position = -1;
+    }
+
+    /**
+     * Adds a Request to the history.
+     *
+     * @param Request $request A Request instance
+     */
+    public function add(Request $request)
+    {
+        $this->stack = array_slice($this->stack, 0, $this->position + 1);
+        $this->stack[] = clone $request;
+        $this->position = count($this->stack) - 1;
+    }
+
+    /**
+     * Returns true if the history is empty.
+     *
+     * @return bool true if the history is empty, false otherwise
+     */
+    public function isEmpty()
+    {
+        return count($this->stack) == 0;
+    }
+
+    /**
+     * Goes back in the history.
+     *
+     * @return Request A Request instance
+     *
+     * @throws \LogicException if the stack is already on the first page
+     */
+    public function back()
+    {
+        if ($this->position < 1) {
+            throw new \LogicException('You are already on the first page.');
+        }
+
+        return clone $this->stack[--$this->position];
+    }
+
+    /**
+     * Goes forward in the history.
+     *
+     * @return Request A Request instance
+     *
+     * @throws \LogicException if the stack is already on the last page
+     */
+    public function forward()
+    {
+        if ($this->position > count($this->stack) - 2) {
+            throw new \LogicException('You are already on the last page.');
+        }
+
+        return clone $this->stack[++$this->position];
+    }
+
+    /**
+     * Returns the current element in the history.
+     *
+     * @return Request A Request instance
+     *
+     * @throws \LogicException if the stack is empty
+     */
+    public function current()
+    {
+        if (-1 == $this->position) {
+            throw new \LogicException('The page history is empty.');
+        }
+
+        return clone $this->stack[$this->position];
+    }
+}