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

vendor/symfony/http-kernel/DependencyInjection/LazyLoadingFragmentHandler.php

@@ -0,0 +1,58 @@
+<?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\HttpKernel\DependencyInjection;
+
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\HttpKernel\Fragment\FragmentHandler;
+
+/**
+ * Lazily loads fragment renderers from the dependency injection container.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class LazyLoadingFragmentHandler extends FragmentHandler
+{
+    private $container;
+    private $rendererIds = array();
+
+    public function __construct(ContainerInterface $container, $debug = false, RequestStack $requestStack = null)
+    {
+        $this->container = $container;
+
+        parent::__construct(array(), $debug, $requestStack);
+    }
+
+    /**
+     * Adds a service as a fragment renderer.
+     *
+     * @param string $renderer The render service id
+     */
+    public function addRendererService($name, $renderer)
+    {
+        $this->rendererIds[$name] = $renderer;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function render($uri, $renderer = 'inline', array $options = array())
+    {
+        if (isset($this->rendererIds[$renderer])) {
+            $this->addRenderer($this->container->get($this->rendererIds[$renderer]));
+
+            unset($this->rendererIds[$renderer]);
+        }
+
+        return parent::render($uri, $renderer, $options);
+    }
+}