diff --git a/core/core.services.yml b/core/core.services.yml
index 71eb009..d05e4bf 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -806,7 +806,7 @@ services:
       - { name: event_subscriber }
   form_ajax_subscriber:
     class: Drupal\Core\EventSubscriber\FormAjaxSubscriber
-    arguments: ['@form_ajax_response_handler']
+    arguments: ['@form_ajax_response_builder']
     tags:
       - { name: event_subscriber }
   route_enhancer.lazy_collector:
@@ -879,8 +879,8 @@ services:
   controller.entity_form:
     class: Drupal\Core\Entity\HtmlEntityFormController
     arguments: ['@controller_resolver', '@form_builder', '@entity.manager']
-  form_ajax_response_handler:
-    class: Drupal\Core\Form\FormAjaxResponseHandler
+  form_ajax_response_builder:
+    class: Drupal\Core\Form\FormAjaxResponseBuilder
     arguments: ['@main_content_renderer.ajax', '@current_route_match']
   router_listener:
     class: Symfony\Component\HttpKernel\EventListener\RouterListener
diff --git a/core/lib/Drupal/Core/EventSubscriber/FormAjaxSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/FormAjaxSubscriber.php
index f4cde1e..9bea727 100644
--- a/core/lib/Drupal/Core/EventSubscriber/FormAjaxSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/FormAjaxSubscriber.php
@@ -9,7 +9,7 @@
 
 use Drupal\Core\Ajax\UpdateBuildIdCommand;
 use Drupal\Core\Form\FormAjaxException;
-use Drupal\Core\Form\FormAjaxResponseHandlerInterface;
+use Drupal\Core\Form\FormAjaxResponseBuilderInterface;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
 use Symfony\Component\HttpKernel\KernelEvents;
@@ -25,20 +25,20 @@ class FormAjaxSubscriber implements EventSubscriberInterface {
   const POST_TO_ORIGINAL_URL = 'post_to_original_url';
 
   /**
-   * The form AJAX handler.
+   * The form AJAX response builder.
    *
-   * @var \Drupal\Core\Form\FormAjaxResponseHandlerInterface
+   * @var \Drupal\Core\Form\FormAjaxResponseBuilderInterface
    */
-  protected $formAjaxResponseHandler;
+  protected $formAjaxResponseBuilder;
 
   /**
    * Constructs a new FormAjaxSubscriber.
    *
-   * @param \Drupal\Core\Form\FormAjaxResponseHandlerInterface $form_ajax_response_handler
-   *   The form AJAX handler.
+   * @param \Drupal\Core\Form\FormAjaxResponseBuilderInterface $form_ajax_response_builder
+   *   The form AJAX response builder.
    */
-  public function __construct(FormAjaxResponseHandlerInterface $form_ajax_response_handler) {
-    $this->formAjaxResponseHandler = $form_ajax_response_handler;
+  public function __construct(FormAjaxResponseBuilderInterface $form_ajax_response_builder) {
+    $this->formAjaxResponseBuilder = $form_ajax_response_builder;
   }
 
   /**
@@ -60,7 +60,7 @@ public function onException(GetResponseForExceptionEvent $event) {
         // If the form build ID has changed, issue an Ajax command to update it.
         $commands[] = new UpdateBuildIdCommand($form_build_id, $form['#build_id']);
       }
-      $response = $this->formAjaxResponseHandler->buildResponse($request, $form, $form_state, $commands);
+      $response = $this->formAjaxResponseBuilder->buildResponse($request, $form, $form_state, $commands);
       // Since this response is being set in place of an exception, explicitly
       // mark this as a 200 status.
       $response->headers->set('X-Status-Code', 200);
diff --git a/core/lib/Drupal/Core/Form/FormAjaxResponseHandler.php b/core/lib/Drupal/Core/Form/FormAjaxResponseBuilder.php
similarity index 91%
rename from core/lib/Drupal/Core/Form/FormAjaxResponseHandler.php
rename to core/lib/Drupal/Core/Form/FormAjaxResponseBuilder.php
index 39919a3..c8b2940 100644
--- a/core/lib/Drupal/Core/Form/FormAjaxResponseHandler.php
+++ b/core/lib/Drupal/Core/Form/FormAjaxResponseBuilder.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Form\FormAjaxResponseHandler.
+ * Contains \Drupal\Core\Form\FormAjaxResponseBuilder.
  */
 
 namespace Drupal\Core\Form;
@@ -14,12 +14,12 @@
 use Symfony\Component\HttpKernel\Exception\HttpException;
 
 /**
- * Handles AJAX form responses.
+ * Builds an AJAX form response.
  *
  * Given the current request, a form render array, its form state, and any AJAX
- * commands to apply to the form, generate a response object.
+ * commands to apply to the form, build a response object.
  */
-class FormAjaxResponseHandler implements FormAjaxResponseHandlerInterface {
+class FormAjaxResponseBuilder implements FormAjaxResponseBuilderInterface {
 
   /**
    * The main content to AJAX Response renderer.
@@ -36,7 +36,7 @@ class FormAjaxResponseHandler implements FormAjaxResponseHandlerInterface {
   protected $routeMatch;
 
   /**
-   * Constructs a new FormAjaxResponseHandler.
+   * Constructs a new FormAjaxResponseBuilder.
    *
    * @param \Drupal\Core\Render\MainContent\MainContentRendererInterface $ajax_renderer
    *   The ajax renderer.
diff --git a/core/lib/Drupal/Core/Form/FormAjaxResponseHandlerInterface.php b/core/lib/Drupal/Core/Form/FormAjaxResponseBuilderInterface.php
similarity index 81%
rename from core/lib/Drupal/Core/Form/FormAjaxResponseHandlerInterface.php
rename to core/lib/Drupal/Core/Form/FormAjaxResponseBuilderInterface.php
index 7582d8c..8822a33 100644
--- a/core/lib/Drupal/Core/Form/FormAjaxResponseHandlerInterface.php
+++ b/core/lib/Drupal/Core/Form/FormAjaxResponseBuilderInterface.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Form\FormAjaxResponseHandlerInterface.
+ * Contains \Drupal\Core\Form\FormAjaxResponseBuilderInterface.
  */
 
 namespace Drupal\Core\Form;
@@ -10,9 +10,9 @@
 use Symfony\Component\HttpFoundation\Request;
 
 /**
- * Provides an interface for handling AJAX form responses.
+ * Provides an interface for building AJAX form responses.
  */
-interface FormAjaxResponseHandlerInterface {
+interface FormAjaxResponseBuilderInterface {
 
   /**
    * Builds a response for an AJAX form.
diff --git a/core/modules/file/src/Controller/FileWidgetAjaxController.php b/core/modules/file/src/Controller/FileWidgetAjaxController.php
index 2252033..6cc1391 100644
--- a/core/modules/file/src/Controller/FileWidgetAjaxController.php
+++ b/core/modules/file/src/Controller/FileWidgetAjaxController.php
@@ -10,7 +10,7 @@
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Ajax\AjaxResponse;
 use Drupal\Core\Ajax\ReplaceCommand;
-use Drupal\Core\Form\FormAjaxResponseHandlerInterface;
+use Drupal\Core\Form\FormAjaxResponseBuilderInterface;
 use Drupal\Core\Form\FormBuilderInterface;
 use Drupal\Core\Render\RendererInterface;
 use Drupal\system\Controller\FormAjaxController;
@@ -39,13 +39,13 @@ class FileWidgetAjaxController extends FormAjaxController {
    *   A logger instance.
    * @param \Drupal\Core\Form\FormBuilderInterface $form_builder
    *   The form builder.
-   * @param \Drupal\Core\Form\FormAjaxResponseHandlerInterface $form_ajax_response_handler
-   *   The form AJAX response handler.
+   * @param \Drupal\Core\Form\FormAjaxResponseBuilderInterface $form_ajax_response_builder
+   *   The form AJAX response builder.
    * @param \Drupal\Core\Render\RendererInterface $renderer
    *   The renderer.
    */
-  public function __construct(LoggerInterface $logger, FormBuilderInterface $form_builder, FormAjaxResponseHandlerInterface $form_ajax_response_handler, RendererInterface $renderer) {
-    parent::__construct($logger, $form_builder, $form_ajax_response_handler);
+  public function __construct(LoggerInterface $logger, FormBuilderInterface $form_builder, FormAjaxResponseBuilderInterface $form_ajax_response_builder, RendererInterface $renderer) {
+    parent::__construct($logger, $form_builder, $form_ajax_response_builder);
     $this->renderer = $renderer;
   }
 
@@ -56,7 +56,7 @@ public static function create(ContainerInterface $container) {
     return new static(
       $container->get('logger.factory')->get('ajax'),
       $container->get('form_builder'),
-      $container->get('form_ajax_response_handler'),
+      $container->get('form_ajax_response_builder'),
       $container->get('renderer')
     );
   }
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index a206f0e..f296702 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -2625,7 +2625,10 @@ protected function prepareRequestForGenerator($clean_urls = TRUE, $override_serv
   protected function buildUrl($path, array $options = array()) {
     if ($path instanceof Url) {
       $absolute_path = clone $path;
-      return $absolute_path->setAbsolute()->toString();
+      return $absolute_path
+        ->setOptions($options)
+        ->setAbsolute()
+        ->toString();
     }
     // The URL generator service is not necessarily available yet; e.g., in
     // interactive installer tests.
diff --git a/core/modules/system/src/Controller/FormAjaxController.php b/core/modules/system/src/Controller/FormAjaxController.php
index ce64867..9f6ca98 100644
--- a/core/modules/system/src/Controller/FormAjaxController.php
+++ b/core/modules/system/src/Controller/FormAjaxController.php
@@ -9,7 +9,7 @@
 
 use Drupal\Core\Ajax\UpdateBuildIdCommand;
 use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
-use Drupal\Core\Form\FormAjaxResponseHandlerInterface;
+use Drupal\Core\Form\FormAjaxResponseBuilderInterface;
 use Drupal\Core\Form\FormState;
 use Drupal\Core\Form\FormBuilderInterface;
 use Drupal\system\FileAjaxForm;
@@ -38,11 +38,11 @@ class FormAjaxController implements ContainerInjectionInterface {
   protected $formBuilder;
 
   /**
-   * The form AJAX response handler.
+   * The form AJAX response builder.
    *
-   * @var \Drupal\Core\Form\FormAjaxResponseHandlerInterface
+   * @var \Drupal\Core\Form\FormAjaxResponseBuilderInterface
    */
-  protected $formAjaxResponseHandler;
+  protected $formAjaxResponseBuilder;
 
   /**
    * Constructs a FormAjaxController object.
@@ -51,13 +51,13 @@ class FormAjaxController implements ContainerInjectionInterface {
    *   A logger instance.
    * @param \Drupal\Core\Form\FormBuilderInterface $form_builder
    *   The form builder.
-   * @param \Drupal\Core\Form\FormAjaxResponseHandlerInterface $form_ajax_response_handler
-   *   The form AJAX response handler.
+   * @param \Drupal\Core\Form\FormAjaxResponseBuilderInterface $form_ajax_response_builder
+   *   The form AJAX response builder.
    */
-  public function __construct(LoggerInterface $logger, FormBuilderInterface $form_builder, FormAjaxResponseHandlerInterface $form_ajax_response_handler) {
+  public function __construct(LoggerInterface $logger, FormBuilderInterface $form_builder, FormAjaxResponseBuilderInterface $form_ajax_response_builder) {
     $this->logger = $logger;
     $this->formBuilder = $form_builder;
-    $this->formAjaxResponseHandler = $form_ajax_response_handler;
+    $this->formAjaxResponseBuilder = $form_ajax_response_builder;
   }
 
   /**
@@ -67,7 +67,7 @@ public static function create(ContainerInterface $container) {
     return new static(
       $container->get('logger.factory')->get('ajax'),
       $container->get('form_builder'),
-      $container->get('form_ajax_response_handler')
+      $container->get('form_ajax_response_builder')
     );
   }
 
@@ -95,7 +95,7 @@ public function content(Request $request) {
 
     $this->formBuilder->processForm($form['#form_id'], $form, $form_state);
 
-    return $this->formAjaxResponseHandler->buildResponse($request, $form, $form_state, $commands);
+    return $this->formAjaxResponseBuilder->buildResponse($request, $form, $form_state, $commands);
   }
 
   /**
diff --git a/core/modules/system/tests/modules/ajax_forms_test/src/Form/AjaxFormsTestSimpleForm.php b/core/modules/system/tests/modules/ajax_forms_test/src/Form/AjaxFormsTestSimpleForm.php
index 225664d..73d5b90 100644
--- a/core/modules/system/tests/modules/ajax_forms_test/src/Form/AjaxFormsTestSimpleForm.php
+++ b/core/modules/system/tests/modules/ajax_forms_test/src/Form/AjaxFormsTestSimpleForm.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Form\FormBase;
 use Drupal\ajax_forms_test\Callbacks;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
 
 /**
  * Form builder: Builds a form that triggers a simple AJAX callback.
@@ -68,7 +69,12 @@ public function buildForm(array $form, FormStateInterface $form_state) {
         '#type' => 'select',
         '#title' => $this->t('Test %key callbacks', array('%key' => $key)),
         '#options' => array('red' => 'red'),
-        '#ajax' => array('callback' => $value),
+        '#ajax' => array(
+          'callback' => $value,
+          // @todo Remove this.
+          'url' => Url::fromRoute('system.ajax'),
+          'cache_form' => TRUE,
+        ),
       );
     }
 
diff --git a/core/tests/Drupal/Tests/Core/EventSubscriber/FormAjaxSubscriberTest.php b/core/tests/Drupal/Tests/Core/EventSubscriber/FormAjaxSubscriberTest.php
index 483c677..14ce121 100644
--- a/core/tests/Drupal/Tests/Core/EventSubscriber/FormAjaxSubscriberTest.php
+++ b/core/tests/Drupal/Tests/Core/EventSubscriber/FormAjaxSubscriberTest.php
@@ -29,9 +29,9 @@ class FormAjaxSubscriberTest extends UnitTestCase {
   protected $subscriber;
 
   /**
-   * @var \Drupal\Core\Form\FormAjaxResponseHandlerInterface|\PHPUnit_Framework_MockObject_MockObject
+   * @var \Drupal\Core\Form\FormAjaxResponseBuilderInterface|\PHPUnit_Framework_MockObject_MockObject
    */
-  protected $formAjaxResponseHandler;
+  protected $formAjaxResponseBuilder;
 
   /**
    * @var \Symfony\Component\HttpKernel\HttpKernelInterface|\PHPUnit_Framework_MockObject_MockObject
@@ -45,8 +45,8 @@ protected function setUp() {
     parent::setUp();
 
     $this->httpKernel = $this->getMock('Symfony\Component\HttpKernel\HttpKernelInterface');
-    $this->formAjaxResponseHandler = $this->getMock('Drupal\Core\Form\FormAjaxResponseHandlerInterface');
-    $this->subscriber = new FormAjaxSubscriber($this->formAjaxResponseHandler);
+    $this->formAjaxResponseBuilder = $this->getMock('Drupal\Core\Form\FormAjaxResponseBuilderInterface');
+    $this->subscriber = new FormAjaxSubscriber($this->formAjaxResponseBuilder);
   }
 
   /**
@@ -61,7 +61,7 @@ public function testOnException() {
     $commands = [];
     $response = new Response('');
 
-    $this->formAjaxResponseHandler->expects($this->once())
+    $this->formAjaxResponseBuilder->expects($this->once())
       ->method('buildResponse')
       ->with($request, $form, $form_state, $commands)
       ->willReturn($response);
@@ -86,7 +86,7 @@ public function testOnExceptionNewBuildId() {
     $commands[] = new UpdateBuildIdCommand('a_new_build_id', 'the_build_id');
     $response = new Response('');
 
-    $this->formAjaxResponseHandler->expects($this->once())
+    $this->formAjaxResponseBuilder->expects($this->once())
       ->method('buildResponse')
       ->with($request, $form, $form_state, $commands)
       ->willReturn($response);
@@ -106,7 +106,7 @@ public function testOnExceptionOtherClass() {
     $request = new Request();
     $exception = new \Exception();
 
-    $this->formAjaxResponseHandler->expects($this->never())
+    $this->formAjaxResponseBuilder->expects($this->never())
       ->method('buildResponse');
 
     $event = new GetResponseForExceptionEvent($this->httpKernel, $request, HttpKernelInterface::MASTER_REQUEST, $exception);
diff --git a/core/tests/Drupal/Tests/Core/Form/FormAjaxResponseHandlerTest.php b/core/tests/Drupal/Tests/Core/Form/FormAjaxResponseBuilderTest.php
similarity index 80%
rename from core/tests/Drupal/Tests/Core/Form/FormAjaxResponseHandlerTest.php
rename to core/tests/Drupal/Tests/Core/Form/FormAjaxResponseBuilderTest.php
index 3568dfe..ba09680 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormAjaxResponseHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormAjaxResponseBuilderTest.php
@@ -2,24 +2,24 @@
 
 /**
  * @file
- * Contains \Drupal\Tests\Core\Form\FormAjaxResponseHandlerTest.
+ * Contains \Drupal\Tests\Core\Form\FormAjaxResponseBuilderTest.
  */
 
 namespace Drupal\Tests\Core\Form;
 
 use Drupal\Core\Ajax\AjaxResponse;
 use Drupal\Core\Ajax\AlertCommand;
-use Drupal\Core\Form\FormAjaxResponseHandler;
+use Drupal\Core\Form\FormAjaxResponseBuilder;
 use Drupal\Core\Form\FormState;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Tests\UnitTestCase;
 use Symfony\Component\HttpFoundation\Request;
 
 /**
- * @coversDefaultClass \Drupal\Core\Form\FormAjaxResponseHandler
+ * @coversDefaultClass \Drupal\Core\Form\FormAjaxResponseBuilder
  * @group Form
  */
-class FormAjaxResponseHandlerTest extends UnitTestCase {
+class FormAjaxResponseBuilderTest extends UnitTestCase {
 
   /**
    * @var \Drupal\Core\Render\MainContent\MainContentRendererInterface|\PHPUnit_Framework_MockObject_MockObject
@@ -32,9 +32,9 @@ class FormAjaxResponseHandlerTest extends UnitTestCase {
   protected $routeMatch;
 
   /**
-   * @var \Drupal\Core\Form\FormAjaxResponseHandler
+   * @var \Drupal\Core\Form\FormAjaxResponseBuilder
    */
-  protected $handler;
+  protected $formAjaxResponseBuilder;
 
   /**
    * {@inheritdoc}
@@ -43,7 +43,7 @@ protected function setUp() {
     parent::setUp();
     $this->renderer = $this->getMock('Drupal\Core\Render\MainContent\MainContentRendererInterface');
     $this->routeMatch = $this->getMock('Drupal\Core\Routing\RouteMatchInterface');
-    $this->handler = new FormAjaxResponseHandler($this->renderer, $this->routeMatch);
+    $this->formAjaxResponseBuilder = new FormAjaxResponseBuilder($this->renderer, $this->routeMatch);
   }
 
   /**
@@ -61,7 +61,7 @@ public function testBuildResponseNoTriggeringElement() {
     $commands = [];
 
     $expected = [];
-    $this->assertSame($expected, $this->handler->buildResponse($request, $form, $form_state, $commands));
+    $this->assertSame($expected, $this->formAjaxResponseBuilder->buildResponse($request, $form, $form_state, $commands));
   }
 
   /**
@@ -81,7 +81,7 @@ public function testBuildResponseNoCallable() {
     $commands = [];
 
     $expected = [];
-    $this->assertSame($expected, $this->handler->buildResponse($request, $form, $form_state, $commands));
+    $this->assertSame($expected, $this->formAjaxResponseBuilder->buildResponse($request, $form, $form_state, $commands));
   }
 
   /**
@@ -110,7 +110,7 @@ public function testBuildResponseRenderArray() {
       ->with($form['test'], $request, $this->routeMatch)
       ->willReturn(new AjaxResponse([]));
 
-    $result = $this->handler->buildResponse($request, $form, $form_state, $commands);
+    $result = $this->formAjaxResponseBuilder->buildResponse($request, $form, $form_state, $commands);
     $this->assertInstanceOf('\Drupal\Core\Ajax\AjaxResponse', $result);
     $this->assertSame($commands, $result->getCommands());
   }
@@ -135,7 +135,7 @@ public function testBuildResponseResponse() {
     $this->renderer->expects($this->never())
       ->method('renderResponse');
 
-    $result = $this->handler->buildResponse($request, $form, $form_state, $commands);
+    $result = $this->formAjaxResponseBuilder->buildResponse($request, $form, $form_state, $commands);
     $this->assertInstanceOf('\Drupal\Core\Ajax\AjaxResponse', $result);
     $this->assertSame($commands, $result->getCommands());
   }
@@ -168,7 +168,7 @@ public function testBuildResponseWithCommands() {
     $this->renderer->expects($this->never())
       ->method('renderResponse');
 
-    $result = $this->handler->buildResponse($request, $form, $form_state, $commands);
+    $result = $this->formAjaxResponseBuilder->buildResponse($request, $form, $form_state, $commands);
     $this->assertInstanceOf('\Drupal\Core\Ajax\AjaxResponse', $result);
     $this->assertSame($commands_expected, $result->getCommands());
   }