diff --git a/core/modules/system/src/Tests/Ajax/DialogTest.php b/core/modules/system/src/Tests/Ajax/DialogTest.php
index f684251..3b77798a 100644
--- a/core/modules/system/src/Tests/Ajax/DialogTest.php
+++ b/core/modules/system/src/Tests/Ajax/DialogTest.php
@@ -32,7 +32,7 @@ public function testDialog() {
     $this->drupalGet('ajax-test/dialog');
 
     // Set up variables for this test.
-    $dialog_renderable = ajax_test_dialog_contents();
+    $dialog_renderable = \Drupal\ajax_test\Controller\AjaxTestController::dialogContents();
     $dialog_contents = drupal_render($dialog_renderable);
     $modal_expected_response = array(
       'command' => 'openDialog',
diff --git a/core/modules/system/tests/modules/ajax_test/ajax_test.module b/core/modules/system/tests/modules/ajax_test/ajax_test.module
index d1faba3..de741fe 100644
--- a/core/modules/system/tests/modules/ajax_test/ajax_test.module
+++ b/core/modules/system/tests/modules/ajax_test/ajax_test.module
@@ -29,31 +29,6 @@ function ajax_test_error() {
 }
 
 /**
- * Returns example content for dialog tests.
- */
-function ajax_test_dialog_contents() {
-  // This is a regular render array; the keys do not have special meaning.
-  $content = array(
-    '#title' => 'AJAX Dialog contents',
-    'content' => array(
-      '#markup' => 'Example message',
-    ),
-    'cancel' => array(
-      '#type' => 'link',
-      '#title' => 'Cancel',
-      '#url' => Url::fromRoute('<front>'),
-      '#attributes' => array(
-        // This is a special class to which JavaScript assigns dialog closing
-        // behavior.
-        'class' => array('dialog-cancel'),
-      ),
-    ),
-  );
-
-  return $content;
-}
-
-/**
  * Menu callback: Close the ajax dialog.
  *
  * @deprecated \Drupal\ajax_test\Controller\AjaxTestController::dialogClose()
diff --git a/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
index c4d40bd..928b84e 100644
--- a/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
+++ b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
@@ -17,11 +17,31 @@
 class AjaxTestController {
 
   /**
-   * Returns example content for dialog testing.
+   * Example content for dialog testing.
+   *
+   * @return array
+   *   Renderable array of AJAX dialog contents.
    */
-  public function dialogContents() {
-    // Re-use the utility method that returns the example content.
-    return ajax_test_dialog_contents();
+  public static function dialogContents() {
+    // This is a regular render array; the keys do not have special meaning.
+    $content = array(
+      '#title' => 'AJAX Dialog contents',
+      'content' => array(
+        '#markup' => 'Example message',
+      ),
+      'cancel' => array(
+        '#type' => 'link',
+        '#title' => 'Cancel',
+        '#url' => Url::fromRoute('<front>'),
+        '#attributes' => array(
+          // This is a special class to which JavaScript assigns dialog closing
+          // behavior.
+          'class' => array('dialog-cancel'),
+        ),
+      ),
+    );
+
+    return $content;
   }
 
   /**
diff --git a/core/modules/system/tests/modules/ajax_test/src/Form/AjaxTestDialogForm.php b/core/modules/system/tests/modules/ajax_test/src/Form/AjaxTestDialogForm.php
index b8a7ad4..922ef60 100644
--- a/core/modules/system/tests/modules/ajax_test/src/Form/AjaxTestDialogForm.php
+++ b/core/modules/system/tests/modules/ajax_test/src/Form/AjaxTestDialogForm.php
@@ -7,9 +7,8 @@
 
 namespace Drupal\ajax_test\Form;
 
-use Drupal\Core\Form\FormInterface;
+use Drupal\ajax_test\Controller\AjaxTestController;
 use Drupal\Core\Form\FormBase;
-use Drupal\Component\Utility\String;
 use Drupal\Core\Ajax\AjaxResponse;
 use Drupal\Core\Ajax\OpenModalDialogCommand;
 use Drupal\Core\Ajax\OpenDialogCommand;
@@ -97,7 +96,7 @@ public function nonModal(&$form, FormStateInterface $form_state) {
    *   An ajax response object.
    */
   protected function dialog($is_modal = FALSE) {
-    $content = ajax_test_dialog_contents();
+    $content = AjaxTestController::dialogContents();
     $response = new AjaxResponse();
     $title = $this->t('AJAX Dialog contents');