Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/node/src/Controller/NodeViewController.php

@@ -0,0 +1,63 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\node\Controller\NodeViewController.
+ */
+
+namespace Drupal\node\Controller;
+
+use Drupal\Component\Utility\SafeMarkup;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\Controller\EntityViewController;
+
+/**
+ * Defines a controller to render a single node.
+ */
+class NodeViewController extends EntityViewController {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function view(EntityInterface $node, $view_mode = 'full', $langcode = NULL) {
+    $build = parent::view($node);
+
+    foreach ($node->uriRelationships() as $rel) {
+      // Set the node path as the canonical URL to prevent duplicate content.
+      $build['#attached']['html_head_link'][] = array(
+        array(
+          'rel' => $rel,
+          'href' => $node->url($rel),
+        ),
+        TRUE,
+      );
+
+      if ($rel == 'canonical') {
+        // Set the non-aliased canonical path as a default shortlink.
+        $build['#attached']['html_head_link'][] = array(
+          array(
+            'rel' => 'shortlink',
+            'href' => $node->url($rel, array('alias' => TRUE)),
+          ),
+          TRUE,
+        );
+      }
+    }
+
+    return $build;
+  }
+
+  /**
+   * The _title_callback for the page that renders a single node.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $node
+   *   The current node.
+   *
+   * @return string
+   *   The page title.
+   */
+  public function title(EntityInterface $node) {
+    return SafeMarkup::checkPlain($this->entityManager->getTranslationFromContext($node)->label());
+  }
+
+}