diff --git a/core/core.services.yml b/core/core.services.yml
index 9b0e053..d050591 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -125,9 +125,7 @@ services:
     arguments: ['@form_validator', '@module_handler', '@keyvalue.expirable', '@event_dispatcher', '@url_generator', '@request_stack', '@?csrf_token', '@?http_kernel']
   form_validator:
     class: Drupal\Core\Form\FormValidator
-    arguments: ['@url_generator', '@?csrf_token']
-    calls:
-      - [setRequest, ['@?request=']]
+    arguments: ['@request_stack', '@?csrf_token']
   keyvalue:
     class: Drupal\Core\KeyValueStore\KeyValueFactory
     arguments: ['@service_container', '@settings']
diff --git a/core/includes/form.inc b/core/includes/form.inc
index 0dc41e9..984daf7 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -11,7 +11,7 @@
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Component\Utility\Xss;
 use Drupal\Core\Database\Database;
-use Drupal\Core\Form\FormHelper;
+use Drupal\Core\Form\OptGroup;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Render\Element;
 use Drupal\Core\Template\Attribute;
@@ -346,10 +346,11 @@ function drupal_redirect_form($form_state) {
  * Executes custom validation and submission handlers for a given form.
  *
  * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.
- *   Use \Drupal::formBuilder()->executeSubmitHandlers().
+ *   Use either \Drupal::formBuilder()->executeSubmitHandlers() or
+ *   \Drupal::service('form_validator')->executeValidateHandlers().
  *
  * @see \Drupal\Core\Form\FormBuilderInterface::executeSubmitHandlers()
- * @see \Drupal\Core\Form\FormBuilderInterface::executeValidateHandlers()
+ * @see \Drupal\Core\Form\FormValidatorInterface::executeValidateHandlers()
  */
 function form_execute_handlers($type, &$form, &$form_state) {
   if ($type == 'submit') {
@@ -851,12 +852,10 @@ function form_set_value($element, $value, &$form_state) {
  *   An array with all hierarchical elements flattened to a single array.
  *
  * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.
- *   Use \Drupal\Core\Form\FormHelper::flattenOptions().
- *
- * @see \Drupal\Core\Form\FormBuilderInterface::flattenOptions().
+ *   Use \Drupal\Core\Form\OptGroup::flattenOptions().
  */
 function form_options_flatten($array) {
-  return FormHelper::flattenOptions($array);
+  return OptGroup::flattenOptions($array);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Form/FormBuilderInterface.php b/core/lib/Drupal/Core/Form/FormBuilderInterface.php
index f13f707..1e43984 100644
--- a/core/lib/Drupal/Core/Form/FormBuilderInterface.php
+++ b/core/lib/Drupal/Core/Form/FormBuilderInterface.php
@@ -7,8 +7,6 @@
 
 namespace Drupal\Core\Form;
 
-use Symfony\Component\HttpFoundation\Request;
-
 /**
  * Provides an interface for form building and processing.
  */
diff --git a/core/lib/Drupal/Core/Form/FormValidator.php b/core/lib/Drupal/Core/Form/FormValidator.php
index e10e4fe..2cb1141 100644
--- a/core/lib/Drupal/Core/Form/FormValidator.php
+++ b/core/lib/Drupal/Core/Form/FormValidator.php
@@ -9,12 +9,11 @@
 
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Component\Utility\Unicode;
-use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Access\CsrfTokenGenerator;
 use Drupal\Core\Render\Element;
-use Drupal\Core\Routing\UrlGeneratorInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
-use Symfony\Component\HttpFoundation\Request;
+use Drupal\Core\Form\OptGroup;
+use Symfony\Component\HttpFoundation\RequestStack;
 
 /**
  * Provides validation of form submissions.
@@ -24,13 +23,6 @@ class FormValidator implements FormValidatorInterface {
   use StringTranslationTrait;
 
   /**
-   * The URL generator.
-   *
-   * @var \Drupal\Core\Routing\UrlGeneratorInterface
-   */
-  protected $urlGenerator;
-
-  /**
    * The CSRF token generator to validate the form token.
    *
    * @var \Drupal\Core\Access\CsrfTokenGenerator
@@ -38,22 +30,22 @@ class FormValidator implements FormValidatorInterface {
   protected $csrfToken;
 
   /**
-   * The current request.
+   * The request stack.
    *
-   * @var \Symfony\Component\HttpFoundation\Request
+   * @var \Symfony\Component\HttpFoundation\RequestStack
    */
-  protected $request;
+  protected $requestStack;
 
   /**
    * Constructs a new FormValidator.
    *
-   * @param \Drupal\Core\Routing\UrlGeneratorInterface $url_generator
-   *   The URL generator.
+   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
+   *   The request stack.
    * @param \Drupal\Core\Access\CsrfTokenGenerator $csrf_token
    *   The CSRF token generator.
    */
-  public function __construct(UrlGeneratorInterface $url_generator, CsrfTokenGenerator $csrf_token = NULL) {
-    $this->urlGenerator = $url_generator;
+  public function __construct(RequestStack $request_stack, CsrfTokenGenerator $csrf_token = NULL) {
+    $this->requestStack = $request_stack;
     $this->csrfToken = $csrf_token;
   }
 
@@ -97,9 +89,7 @@ public function validateForm($form_id, &$form, &$form_state) {
     // matches the current user's session.
     if (isset($form['#token'])) {
       if (!$this->csrfToken->validate($form_state['values']['form_token'], $form['#token'])) {
-        $path = $this->request->attributes->get('_system_path');
-        $query = UrlHelper::filterQueryParameters($this->request->query->all());
-        $url = $this->urlGenerator->generateFromPath($path, array('query' => $query));
+        $url = $this->requestStack->getCurrentRequest()->getRequestUri();
 
         // Setting this error will cause the form to fail validation.
         $this->setErrorByName('form_token', $form_state, $this->t('The form has become outdated. Copy any unsaved work in the form below and then <a href="@link">reload this page</a>.', array('@link' => $url)));
@@ -315,7 +305,7 @@ protected function performRequiredValidation(&$elements, &$form_state) {
 
     if (isset($elements['#options']) && isset($elements['#value'])) {
       if ($elements['#type'] == 'select') {
-        $options = FormHelper::flattenOptions($elements['#options']);
+        $options = OptGroup::flattenOptions($elements['#options']);
       }
       else {
         $options = $elements['#options'];
@@ -451,7 +441,7 @@ public function setErrorByName($name, array &$form_state, $message = '') {
       }
       if ($record) {
         $form_state['errors'][$name] = $message;
-        $this->request->attributes->set('_form_errors', TRUE);
+        $this->requestStack->getCurrentRequest()->attributes->set('_form_errors', TRUE);
         if ($message) {
           $this->drupalSetMessage($message, 'error');
         }
@@ -489,7 +479,7 @@ public function getError($element, array &$form_state) {
    */
   public function clearErrors(array &$form_state) {
     $form_state['errors'] = array();
-    $this->request->attributes->set('_form_errors', FALSE);
+    $this->requestStack->getCurrentRequest()->attributes->set('_form_errors', FALSE);
   }
 
   /**
@@ -503,14 +493,7 @@ public function getErrors(array $form_state) {
    * {@inheritdoc}
    */
   public function getAnyErrors() {
-    return (bool) $this->request->attributes->get('_form_errors');
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function setRequest(Request $request) {
-    $this->request = $request;
+    return (bool) $this->requestStack->getCurrentRequest()->attributes->get('_form_errors');
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Form/FormValidatorInterface.php b/core/lib/Drupal/Core/Form/FormValidatorInterface.php
index 4de9bfa..806e6a0 100644
--- a/core/lib/Drupal/Core/Form/FormValidatorInterface.php
+++ b/core/lib/Drupal/Core/Form/FormValidatorInterface.php
@@ -7,8 +7,6 @@
 
 namespace Drupal\Core\Form;
 
-use Symfony\Component\HttpFoundation\Request;
-
 /**
  * Provides an interface for validating form submissions.
  */
@@ -56,12 +54,4 @@ public function executeValidateHandlers(&$form, &$form_state);
    */
   public function validateForm($form_id, &$form, &$form_state);
 
-  /**
-   * Sets the request object to use.
-   *
-   * @param \Symfony\Component\HttpFoundation\Request $request
-   *   The request object.
-   */
-  public function setRequest(Request $request);
-
 }
diff --git a/core/lib/Drupal/Core/Form/FormHelper.php b/core/lib/Drupal/Core/Form/OptGroup.php
similarity index 92%
rename from core/lib/Drupal/Core/Form/FormHelper.php
rename to core/lib/Drupal/Core/Form/OptGroup.php
index 833160f..f94d62d 100644
--- a/core/lib/Drupal/Core/Form/FormHelper.php
+++ b/core/lib/Drupal/Core/Form/OptGroup.php
@@ -2,15 +2,15 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Form\FormHelper.
+ * Contains \Drupal\Core\Form\OptGroup.
  */
 
 namespace Drupal\Core\Form;
 
 /**
- * Provides utility methods used by form processing.
+ * Provides helpers for HTML option groups.
  */
-class FormHelper {
+class OptGroup {
 
   /**
    * Allows PHP array processing of multiple select options with the same value.
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/ConfigurableEntityReferenceItem.php b/core/modules/entity_reference/lib/Drupal/entity_reference/ConfigurableEntityReferenceItem.php
index f03f829..4757302 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/ConfigurableEntityReferenceItem.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/ConfigurableEntityReferenceItem.php
@@ -10,7 +10,7 @@
 use Drupal\Component\Utility\String;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
-use Drupal\Core\Form\FormHelper;
+use Drupal\Core\Form\OptGroup;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\TypedData\AllowedValuesInterface;
 use Drupal\Core\TypedData\DataDefinition;
@@ -70,7 +70,7 @@ public function getPossibleOptions(AccountInterface $account = NULL) {
   public function getSettableValues(AccountInterface $account = NULL) {
     // Flatten options first, because "settable options" may contain group
     // arrays.
-    $flatten_options = FormHelper::flattenOptions($this->getSettableOptions($account));
+    $flatten_options = OptGroup::flattenOptions($this->getSettableOptions($account));
     return array_keys($flatten_options);
   }
 
diff --git a/core/modules/options/lib/Drupal/options/Plugin/Field/FieldType/ListItemBase.php b/core/modules/options/lib/Drupal/options/Plugin/Field/FieldType/ListItemBase.php
index 5fbf7d2..64604e5 100644
--- a/core/modules/options/lib/Drupal/options/Plugin/Field/FieldType/ListItemBase.php
+++ b/core/modules/options/lib/Drupal/options/Plugin/Field/FieldType/ListItemBase.php
@@ -8,7 +8,7 @@
 namespace Drupal\options\Plugin\Field\FieldType;
 
 use Drupal\Core\Field\FieldItemBase;
-use Drupal\Core\Form\FormHelper;
+use Drupal\Core\Form\OptGroup;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\TypedData\AllowedValuesInterface;
 
@@ -33,7 +33,7 @@ public static function defaultSettings() {
   public function getPossibleValues(AccountInterface $account = NULL) {
     // Flatten options firstly, because Possible Options may contain group
     // arrays.
-    $flatten_options = FormHelper::flattenOptions($this->getPossibleOptions($account));
+    $flatten_options = OptGroup::flattenOptions($this->getPossibleOptions($account));
     return array_keys($flatten_options);
   }
 
@@ -50,7 +50,7 @@ public function getPossibleOptions(AccountInterface $account = NULL) {
   public function getSettableValues(AccountInterface $account = NULL) {
     // Flatten options firstly, because Settable Options may contain group
     // arrays.
-    $flatten_options = FormHelper::flattenOptions($this->getSettableOptions($account));
+    $flatten_options = OptGroup::flattenOptions($this->getSettableOptions($account));
     return array_keys($flatten_options);
   }
 
diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/Field/FieldType/TaxonomyTermReferenceItem.php b/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/Field/FieldType/TaxonomyTermReferenceItem.php
index fc1fa46..cc8ef7e 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/Field/FieldType/TaxonomyTermReferenceItem.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/Field/FieldType/TaxonomyTermReferenceItem.php
@@ -9,7 +9,7 @@
 
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
-use Drupal\Core\Form\FormHelper;
+use Drupal\Core\Form\OptGroup;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\TypedData\AllowedValuesInterface;
 
@@ -49,7 +49,7 @@ public static function defaultSettings() {
   public function getPossibleValues(AccountInterface $account = NULL) {
     // Flatten options firstly, because Possible Options may contain group
     // arrays.
-    $flatten_options = FormHelper::flattenOptions($this->getPossibleOptions($account));
+    $flatten_options = OptGroup::flattenOptions($this->getPossibleOptions($account));
     return array_keys($flatten_options);
   }
 
@@ -66,7 +66,7 @@ public function getPossibleOptions(AccountInterface $account = NULL) {
   public function getSettableValues(AccountInterface $account = NULL) {
     // Flatten options firstly, because Settable Options may contain group
     // arrays.
-    $flatten_options = FormHelper::flattenOptions($this->getSettableOptions($account));
+    $flatten_options = OptGroup::flattenOptions($this->getSettableOptions($account));
     return array_keys($flatten_options);
   }
 
diff --git a/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php b/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
index bd272e0..916ad1d 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
@@ -9,7 +9,7 @@
 
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
-use Drupal\Core\Form\FormHelper;
+use Drupal\Core\Form\OptGroup;
 use Drupal\Core\Form\FormInterface;
 use Drupal\Core\Url;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -478,7 +478,7 @@ public function testRebuildForm() {
    * @dataProvider providerTestFlattenOptions
    */
   public function testFlattenOptions($options) {
-    $this->assertSame(array('foo' => 1), FormHelper::flattenOptions($options));
+    $this->assertSame(array('foo' => 1), OptGroup::flattenOptions($options));
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Core/Form/FormValidatorTest.php b/core/tests/Drupal/Tests/Core/Form/FormValidatorTest.php
index 2a723bb..81bfeb8 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormValidatorTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormValidatorTest.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\String;
 use Drupal\Tests\UnitTestCase;
 use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\RequestStack;
 
 /**
  * Tests the form validator.
@@ -113,11 +114,9 @@ public function testMustValidate() {
    * @covers ::validateForm
    */
   public function testValidateInvalidFormToken() {
-    $url_generator = $this->getMock('Drupal\Core\Routing\UrlGeneratorInterface');
-    $url_generator->expects($this->once())
-      ->method('generateFromPath')
-      ->with('test/example', array('query' => array('foo' => 'bar')))
-      ->will($this->returnValue('/test/example?foo=bar'));
+    $request_stack = new RequestStack();
+    $request = new Request(array(), array(), array(), array(), array(), array('REQUEST_URI' => '/test/example?foo=bar'));
+    $request_stack->push($request);
     $csrf_token = $this->getMockBuilder('Drupal\Core\Access\CsrfTokenGenerator')
       ->disableOriginalConstructor()
       ->getMock();
@@ -126,7 +125,7 @@ public function testValidateInvalidFormToken() {
       ->will($this->returnValue(FALSE));
 
     $form_validator = $this->getMockBuilder('Drupal\Core\Form\FormValidator')
-      ->setConstructorArgs(array($url_generator, $csrf_token))
+      ->setConstructorArgs(array($request_stack, $csrf_token))
       ->setMethods(array('setErrorByName', 't', 'doValidateForm'))
       ->getMock();
     $form_validator->expects($this->once())
@@ -139,8 +138,6 @@ public function testValidateInvalidFormToken() {
       ->with('form_token', $this->isType('array'), 'The form has become outdated. Copy any unsaved work in the form below and then <a href="/test/example?foo=bar">reload this page</a>.');
     $form_validator->expects($this->never())
       ->method('doValidateForm');
-    $request = new Request(array('foo' => 'bar'), array(), array('_system_path' => 'test/example'));
-    $form_validator->setRequest($request);
 
     $form['#token'] = 'test_form_id';
     $form_state = $this->getFormStateDefaults();
@@ -153,7 +150,7 @@ public function testValidateInvalidFormToken() {
    * @covers ::validateForm
    */
   public function testValidateValidFormToken() {
-    $url_generator = $this->getMock('Drupal\Core\Routing\UrlGeneratorInterface');
+    $request_stack = new RequestStack();
     $csrf_token = $this->getMockBuilder('Drupal\Core\Access\CsrfTokenGenerator')
       ->disableOriginalConstructor()
       ->getMock();
@@ -162,7 +159,7 @@ public function testValidateValidFormToken() {
       ->will($this->returnValue(TRUE));
 
     $form_validator = $this->getMockBuilder('Drupal\Core\Form\FormValidator')
-      ->setConstructorArgs(array($url_generator, $csrf_token))
+      ->setConstructorArgs(array($request_stack, $csrf_token))
       ->setMethods(array('setErrorByName', 'doValidateForm'))
       ->getMock();
     $form_validator->expects($this->never())
@@ -237,14 +234,15 @@ public function providerTestGetError() {
    * @dataProvider providerTestSetErrorByName
    */
   public function testSetErrorByName($limit_validation_errors, $expected_errors, $set_message = FALSE) {
+    $request_stack = new RequestStack();
+    $request = new Request();
+    $request_stack->push($request);
     $form_validator = $this->getMockBuilder('Drupal\Core\Form\FormValidator')
-      ->disableOriginalConstructor()
+      ->setConstructorArgs(array($request_stack))
       ->setMethods(array('drupalSetMessage'))
       ->getMock();
     $form_validator->expects($set_message ? $this->once() : $this->never())
       ->method('drupalSetMessage');
-    $request = new Request();
-    $form_validator->setRequest($request);
 
     $form_state = $this->getFormStateDefaults();
     $form_state['limit_validation_errors'] = $limit_validation_errors;
@@ -272,12 +270,13 @@ public function providerTestSetErrorByName() {
    * @covers ::setElementErrorsFromFormState
    */
   public function testSetElementErrorsFromFormState() {
+    $request_stack = new RequestStack();
+    $request = new Request();
+    $request_stack->push($request);
     $form_validator = $this->getMockBuilder('Drupal\Core\Form\FormValidator')
-      ->disableOriginalConstructor()
+      ->setConstructorArgs(array($request_stack))
       ->setMethods(array('drupalSetMessage'))
       ->getMock();
-    $request = new Request();
-    $form_validator->setRequest($request);
 
     $form = array(
       '#parents' => array(),
@@ -439,8 +438,6 @@ public function testRequiredErrorMessage($element, $expected_message) {
     $form_validator->expects($this->once())
       ->method('setErrorByName')
       ->with('test', $this->isType('array'), $expected_message);
-    $request = new Request();
-    $form_validator->setRequest($request);
 
     $form = array();
     $form['test'] = $element + array(
@@ -493,8 +490,6 @@ public function testElementValidate() {
     $mock->expects($this->once())
       ->method('element_validate')
       ->with($this->isType('array'), $this->isType('array'), NULL);
-    $request = new Request();
-    $form_validator->setRequest($request);
 
     $form = array();
     $form['test'] = array(
@@ -517,8 +512,6 @@ public function testPerformRequiredValidation($element, $expected_message, $call
       ->disableOriginalConstructor()
       ->setMethods(array('t', 'setErrorByName', 'watchdog'))
       ->getMock();
-    $request = new Request();
-    $form_validator->setRequest($request);
     $form_validator->expects($this->any())
       ->method('t')
       ->will($this->returnCallback(function ($string, $args) {