reverted:
--- b/core/modules/system/src/EventSubscriber/GroupRouteSubscriber.php
+++ /dev/null
@@ -1,145 +0,0 @@
-<?php
-
-namespace Drupal\system\EventSubscriber;
-
-use Drupal\Core\Routing\RouteSubscriberBase;
-use Symfony\Component\Routing\RouteCollection;
-use Drupal\Core\Access\AccessManagerInterface;
-use Drupal\Core\Entity\EntityTypeManagerInterface;
-use Drupal\Core\Menu\MenuLinkTreeInterface;
-use Drupal\Core\Menu\MenuTreeParameters;
-use Drupal\user\Entity\User;
-
-/**
- * Alters routes, which are parents for other routes.
- */
-class GroupRouteSubscriber extends RouteSubscriberBase {
-
-  /**
-   * The access manager.
-   *
-   * @var \Drupal\Core\Access\AccessManagerInterface
-   */
-  protected $accessManager;
-
-  /**
-   * The menu link tree service.
-   *
-   * @var \Drupal\Core\Menu\MenuLinkTreeInterface
-   */
-  protected $menuLinkTree;
-
-  /**
-   * The entity type manager.
-   *
-   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
-   */
-  protected $entityTypeManager;
-
-  /**
-   * Constructs a new GroupRouteSubscriber.
-   *
-   * @param \Drupal\Core\Access\AccessManagerInterface $access_manager
-   *   The access manager.
-   * @param \Drupal\Core\Menu\MenuLinkTreeInterface $menu_link_tree
-   *   The menu link tree service.
-   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
-   *   The entity type manager.
-   */
-  public function __construct(AccessManagerInterface $access_manager, MenuLinkTreeInterface $menu_link_tree, EntityTypeManagerInterface $entity_type_manager) {
-    $this->accessManager = $access_manager;
-    $this->menuLinkTree = $menu_link_tree;
-    $this->entityTypeManager = $entity_type_manager;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function alterRoutes(RouteCollection $collection) {
-    // Load all roles and leave only non-admin ones with necessary permission.
-    try {
-      $roles = $this->entityTypeManager->getStorage('user_role')->loadMultiple();
-      $user_storage = $this->entityTypeManager->getStorage('user');
-    }
-    catch (\Exception $e) {
-      return;
-    }
-    $access_roles = [];
-    $admin_role = '';
-    foreach ($roles as $role_id => $role) {
-      if ($role->isAdmin()) {
-        $admin_role = $role_id;
-        continue;
-      }
-      if ($role->hasPermission('access administration pages')) {
-        $access_roles[$role_id] = $user_storage->create([
-          'roles' => [
-            $role_id,
-          ],
-        ]);
-      }
-    }
-    if (empty($admin_role) || empty($access_roles)) {
-      return;
-    }
-    foreach ($collection->all() as $route_id => $route) {
-      if ($route->hasOption('_group_route')) {
-        // Add admin role in order to restrict access for other roles.
-        $route_accessible_roles = [$admin_role];
-        // Perform check.
-        $this->checkAccess($route_accessible_roles, $collection, $route_id, NULL, NULL, $access_roles);
-        $route->setRequirement('_role', (string) implode('+', $route_accessible_roles));
-      }
-    }
-  }
-
-  /**
-   * Checks route and its children.
-   *
-   * @param array $route_accessible_roles
-   *   Array with role names, which are allowed to access route.
-   * @param Symfony\Component\Routing\RouteCollection $collection
-   *   Routes collection.
-   * @param string $route_id
-   *   Route ID.
-   * @param Drupal\user\Entity\User $test_user
-   *   User object for test.
-   * @param string $test_role
-   *   User's role to be added in array.
-   * @param array $access_roles
-   *   Array with test users for access checking.
-   */
-  protected function checkAccess(array &$route_accessible_roles, RouteCollection $collection, $route_id, User $test_user = NULL, $test_role = NULL, array $access_roles = NULL) {
-    // Load all menu links below route
-    // and check if route has any accessible children by any of roles.
-    $parameters = new MenuTreeParameters();
-    $parameters->setRoot($route_id)->excludeRoot()->setTopLevelOnly()->onlyEnabledLinks();
-    $tree = $this->menuLinkTree->load(NULL, $parameters);
-    if (empty($tree)) {
-      if ($collection->get($route_id)->hasOption('_group_route')) {
-        return;
-      }
-      $route_accessible_roles[] = $test_role;
-    }
-    else {
-      foreach ($tree as $element_id => $element) {
-        $url = $element->link->getUrlObject();
-        if (!empty($access_roles)) {
-          foreach ($access_roles as $route_role => $role_user) {
-            if ($this->accessManager->checkNamedRoute($url->getRouteName(), $url->getRouteParameters(), $role_user) && !in_array($route_role, $route_accessible_roles)) {
-              // User is allowed to visit this page, but need to check,
-              // if it's also group route with inaccessible children.
-              $this->checkAccess($route_accessible_roles, $collection, $element_id, $role_user, $route_role);
-            }
-          }
-        }
-        else {
-          if ($this->accessManager->checkNamedRoute($url->getRouteName(), $url->getRouteParameters(), $test_user) && !in_array($test_role, $route_accessible_roles)) {
-            $route_accessible_roles[] = $test_role;
-          }
-        }
-      }
-    }
-  }
-
-}
diff -u b/core/modules/system/tests/src/Functional/Menu/MenuAccessTest.php b/core/modules/system/tests/src/Functional/Menu/MenuAccessTest.php
--- b/core/modules/system/tests/src/Functional/Menu/MenuAccessTest.php
+++ b/core/modules/system/tests/src/Functional/Menu/MenuAccessTest.php
@@ -88,7 +88,8 @@
       'label' => 'Test role',
       'id' => 'test_role',
     ];
-    $this->drupalPostform('admin/people/roles/add', $edit, t('Save'));
+    $this->drupalGet('admin/people/roles/add');
+    $this->submitForm($edit, 'Save');
     $this->assertSession()->statusCodeEquals(200);
 
     // Give access to toolbar, theme and admin pages.
@@ -97,7 +98,8 @@
       'test_role[view the administration theme]' => TRUE,
       'test_role[access toolbar]' => TRUE,
     ];
-    $this->drupalPostform('admin/people/permissions/test_role', $edit, t('Save permissions'));
+    $this->drupalGet('admin/people/permissions/test_role');
+    $this->submitForm($edit, 'Save permissions');
     $this->assertSession()->statusCodeEquals(200);
 
     // Create a user with the role created above and login with this user.
@@ -105,7 +107,8 @@
     $edit = [
       'roles[test_role]' => 'test_role',
     ];
-    $this->drupalPostform('user/' . $webUser->id() . '/edit', $edit, t('Save'));
+    $this->drupalGet('user/' . $webUser->id() . '/edit');
+    $this->submitForm($edit, 'Save');
     $this->assertSession()->statusCodeEquals(200);
     $this->drupalLogout();
     $this->drupalLogin($webUser);