diff --git a/core/authorize.php b/core/authorize.php
index 8715fb0..663128c 100644
--- a/core/authorize.php
+++ b/core/authorize.php
@@ -20,6 +20,7 @@
  * @link authorize Authorized operation helper functions @endlink
  */
 
+use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Symfony\Component\HttpFoundation\Request;
 
 // Change the directory to the Drupal root.
@@ -155,13 +156,7 @@ function authorize_access_allowed() {
 
 if (!empty($output)) {
   drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
-  $maintenance_page = array(
-    '#page' => array(
-      '#title' => $page_title,
-    ),
-    '#theme' => 'maintenance_page',
-    '#content' => $output,
+  print DefaultHtmlPageRenderer::renderPage($output, $page_title, 'maintenance', array(
     '#show_messages' => $show_messages,
-  );
-  print drupal_render($maintenance_page);
+  ));
 }
diff --git a/core/includes/batch.inc b/core/includes/batch.inc
index daa7b2f..153a7de 100644
--- a/core/includes/batch.inc
+++ b/core/includes/batch.inc
@@ -16,6 +16,7 @@
 
 use Drupal\Component\Utility\Timer;
 use Drupal\Core\Batch\Percentage;
+use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\RedirectResponse;
@@ -121,18 +122,14 @@ function _batch_progress_page() {
     // the error message.
     ob_start();
     $fallback = $current_set['error_message'] . '<br />' . $batch['error_message'];
-    $fallback = array(
-      '#theme' => 'maintenance_page',
-      '#title' => $current_set['title'],
-      '#content' => $fallback,
-      '#show_messages' => FALSE,
-    );
 
     // We strip the end of the page using a marker in the template, so any
     // additional HTML output by PHP shows up inside the page rather than below
     // it. While this causes invalid HTML, the same would be true if we didn't,
     // as content is not allowed to appear after </html> anyway.
-    $fallback = drupal_render($fallback);
+    $fallback = DefaultHtmlPageRenderer::renderPage($fallback, $current_set['title'], 'maintenance', array(
+      '#show_messages' => FALSE,
+    ));
     list($fallback) = explode('<!--partial-->', $fallback);
     print $fallback;
 
diff --git a/core/includes/common.inc b/core/includes/common.inc
index b7dfde2..cd878c9 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3633,11 +3633,19 @@ function drupal_prepare_page($page) {
     drupal_set_page_content($page);
     $page = element_info('page');
   }
+  // Special front controllers (like install.php and update.php) are returning a
+  // proper #type 'page' render array (in order to set a custom #theme template),
+  // so just ensure that #type 'page' is complete.
+  elseif (isset($page['#type']) && $page['#type'] === 'page') {
+    $page += element_info('page');
+  }
 
   // Modules can add elements to $page as needed in hook_page_build().
-  foreach (\Drupal::moduleHandler()->getImplementations('page_build') as $module) {
-    $function = $module . '_page_build';
-    $function($page);
+  if (!defined('MAINTENANCE_MODE')) {
+    foreach (\Drupal::moduleHandler()->getImplementations('page_build') as $module) {
+      $function = $module . '_page_build';
+      $function($page);
+    }
   }
   // Modules alter the $page as needed. Blocks are populated into regions like
   // 'sidebar_first', 'footer', etc.
@@ -3648,11 +3656,11 @@ function drupal_prepare_page($page) {
   // cache, even though they should be. This happens because they're rendered
   // directly by the theme system.
   // @todo Remove this once https://drupal.org/node/1869476 lands.
-  if (theme_get_setting('features.main_menu') && count(menu_main_menu())) {
+  if (!defined('MAINTENANCE_MODE') && theme_get_setting('features.main_menu') && count(menu_main_menu())) {
     $main_links_source = _menu_get_links_source('main_links', 'main');
     $page['page_top']['#cache']['tags']['menu'][$main_links_source] = $main_links_source;
   }
-  if (theme_get_setting('features.secondary_menu') && count(menu_secondary_menu())) {
+  if (!defined('MAINTENANCE_MODE') && theme_get_setting('features.secondary_menu') && count(menu_secondary_menu())) {
     $secondary_links_source = _menu_get_links_source('secondary_links', 'account');
     $page['page_top']['#cache']['tags']['menu'][$secondary_links_source] = $secondary_links_source;
   }
@@ -3660,7 +3668,7 @@ function drupal_prepare_page($page) {
   // If no module has taken care of the main content, add it to the page now.
   // This allows the site to still be usable even if no modules that
   // control page regions (for example, the Block module) are enabled.
-  if (!$main_content_display) {
+  if (!$main_content_display && !isset($page['content']['system_main'])) {
     $page['content']['system_main'] = drupal_set_page_content();
   }
 
diff --git a/core/includes/errors.inc b/core/includes/errors.inc
index 56c276f..56cf71a 100644
--- a/core/includes/errors.inc
+++ b/core/includes/errors.inc
@@ -5,6 +5,7 @@
  * Functions for error handling.
  */
 
+use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Drupal\Core\Utility\Error;
 use Drupal\Component\Utility\String;
 use Symfony\Component\HttpFoundation\Response;
@@ -231,12 +232,7 @@ function _drupal_log_error($error, $fatal = FALSE) {
         install_display_output($output, $GLOBALS['install_state']);
       }
       else {
-        $output = array(
-          '#theme' => 'maintenance_page',
-          '#title' => 'Error',
-          '#content' => $message,
-        );
-        $output = drupal_render($output);
+        $output = DefaultHtmlPageRenderer::renderPage($message, 'Error');
       }
 
       $response = new Response($output, 500);
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index e534003..1cb6ab5 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -14,6 +14,7 @@
 use Drupal\Core\Installer\Exception\NoProfilesException;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Language\LanguageManager;
+use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Drupal\Core\StringTranslation\Translator\FileTranslation;
 use Drupal\Core\Extension\ExtensionDiscovery;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
@@ -899,6 +900,7 @@ function install_display_output($output, $install_state) {
   // Only show the task list if there is an active task; otherwise, the page
   // request has ended before tasks have even been started, so there is nothing
   // meaningful to show.
+  $regions = array();
   if (isset($install_state['active_task'])) {
     // Let the theming function know when every step of the installation has
     // been completed.
@@ -909,20 +911,10 @@ function install_display_output($output, $install_state) {
       '#active' => $active_task,
       '#variant' => 'install',
     );
-    drupal_add_region_content('sidebar_first', drupal_render($task_list));
+    $regions['sidebar_first'] = $task_list;
   }
-  $install_page = array(
-    '#theme' => 'install_page',
-    // $output has to be rendered here, because the install page template is not
-    // wrapped into the html template, which means that any #attached libraries
-    // in $output will not be loaded, because the wrapping HTML has been printed
-    // already.
-    '#content' => drupal_render($output),
-  );
-  if (isset($output['#title'])) {
-    $install_page['#page']['#title'] = $output['#title'];
-  }
-  print drupal_render($install_page);
+
+  print DefaultHtmlPageRenderer::renderPage($output, $output['#title'], 'install', $regions);
   exit;
 }
 
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index f699d4b..09488f0 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2074,16 +2074,26 @@ function template_preprocess_page(&$variables) {
 
   $variables['base_path']         = base_path();
   $variables['front_page']        = url();
-  $variables['feed_icons']        = drupal_get_feeds();
   $variables['language']          = $language_interface;
   $variables['language']->dir     = $language_interface->direction ? 'rtl' : 'ltr';
   $variables['logo']              = theme_get_setting('logo.url');
-  $variables['main_menu']         = theme_get_setting('features.main_menu') ? menu_main_menu() : array();
-  $variables['secondary_menu']    = theme_get_setting('features.secondary_menu') ? menu_secondary_menu() : array();
-  $variables['action_links']      = menu_get_local_actions();
   $variables['site_name']         = (theme_get_setting('features.name') ? String::checkPlain($site_config->get('name')) : '');
   $variables['site_slogan']       = (theme_get_setting('features.slogan') ? filter_xss_admin($site_config->get('slogan')) : '');
-  $variables['tabs']              = menu_local_tabs();
+
+  if (!defined('MAINTENANCE_MODE')) {
+    $variables['main_menu']      = theme_get_setting('features.main_menu') ? menu_main_menu() : array();
+    $variables['secondary_menu'] = theme_get_setting('features.secondary_menu') ? menu_secondary_menu() : array();
+    $variables['action_links']   = menu_get_local_actions();
+    $variables['tabs']           = menu_local_tabs();
+    $variables['feed_icons']     = drupal_get_feeds();
+  }
+  else {
+    $variables['main_menu']      = array();
+    $variables['secondary_menu'] = array();
+    $variables['action_links']   = array();
+    $variables['tabs']           = array();
+    $variables['feed_icons']     = '';
+  }
 
   // Pass the main menu and secondary menu to the template as render arrays.
   if (!empty($variables['main_menu'])) {
@@ -2124,10 +2134,12 @@ function template_preprocess_page(&$variables) {
   // re-use the cache of an already retrieved menu containing the active link
   // for the current page.
   // @see menu_tree_page_data()
-  $variables['breadcrumb'] = array(
-    '#theme' => 'breadcrumb',
-    '#breadcrumb' => \Drupal::service('breadcrumb')->build(\Drupal::request()->attributes->all()),
-  );
+  if (!defined('MAINTENANCE_MODE')) {
+    $variables['breadcrumb'] = array(
+      '#theme' => 'breadcrumb',
+      '#breadcrumb' => \Drupal::service('breadcrumb')->build(\Drupal::request()->attributes->all()),
+    );
+  }
 }
 
 /**
@@ -2205,12 +2217,6 @@ function theme_get_suggestions($args, $base, $delimiter = '__') {
  *
  * Default template: maintenance-page.html.twig.
  *
- * The variables array generated here is a mirror of
- * template_preprocess_page(). This preprocessor will run its course when
- * theme_maintenance_page() is invoked. An alternate template file of
- * maintenance-page--offline.html.twig can be used when the database is offline
- * to hide errors and completely replace the content.
- *
  * @param array $variables
  *   An associative array containing:
  *   - content - An array of page content.
@@ -2218,117 +2224,29 @@ function theme_get_suggestions($args, $base, $delimiter = '__') {
  * @see system_page_build()
  */
 function template_preprocess_maintenance_page(&$variables) {
-  $language_interface = \Drupal::languageManager()->getCurrentLanguage();
-
-  // Initializes attributes which are specific to the html element.
-  $variables['html_attributes'] = new Attribute;
-
-  // HTML element attributes.
-  $variables['html_attributes']['lang'] = $language_interface->id;
-  $variables['html_attributes']['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
-
-  // Add favicon
-  if (theme_get_setting('features.favicon')) {
-    $favicon = theme_get_setting('favicon.url');
-    $type = theme_get_setting('favicon.mimetype');
-    $build['#attached']['drupal_add_html_head_link'][][] = array(
-      'rel' => 'shortcut icon',
-      'href' => UrlHelper::stripDangerousProtocols($favicon),
-      'type' => $type,
-    );
-    drupal_render($build);
-  }
-
-  foreach (system_region_list($GLOBALS['theme']) as $region_key => $region_name) {
-    if (!isset($variables[$region_key])) {
-      $variables[$region_key] = array();
-    }
-    // Append region content set with drupal_add_region_content() as markup.
-    if ($region_content = drupal_get_region_content($region_key)) {
-      $variables[$region_key][]['#markup'] = $region_content;
-    }
-  }
-
-  // Setup layout variable.
-  $variables['layout'] = 'none';
-  if (!empty($variables['sidebar_first'])) {
-    $variables['layout'] = 'first';
-  }
-  if (!empty($variables['sidebar_second'])) {
-    $variables['layout'] = ($variables['layout'] == 'first') ? 'both' : 'second';
-  }
-
-  $site_config = \Drupal::config('system.site');
-  $site_name = $site_config->get('name');
-  $site_slogan = $site_config->get('slogan');
-
-   // Construct the page title.
-  if (isset($variables['page']['#title'])) {
-    $head_title = array(
-      'title' => strip_tags($variables['page']['#title']),
-      'name' => String::checkPlain($site_config->get('name')),
-    );
-  }
-  else {
-    $head_title = array('name' => String::checkPlain($site_name));
-    if ($site_slogan) {
-      $head_title['slogan'] = strip_tags(filter_xss_admin($site_slogan));
-    }
-  }
-
-  // These are usually added from system_page_build() except maintenance.css.
-  // When the database is inactive it's not called so we add it here.
-  $default_css['library'][] = 'core/normalize';
-  $default_css['library'][] = 'system/maintenance';
-  $attached = array('#attached' => $default_css);
-  drupal_render($attached);
-  $variables['messages'] = array(
-    '#theme' => 'status_messages',
-    '#access' => $variables['show_messages'],
-  );
-
-  $variables['head_title_array']  = $head_title;
-  $variables['head_title']        = implode(' | ', $head_title);
-  $variables['front_page']        = url();
-  $variables['help']              = '';
-  $variables['language']          = $language_interface;
-  $variables['logo']              = theme_get_setting('logo.url');
-  $variables['site_name']         = (theme_get_setting('features.name') ? String::checkPlain($site_name) : '');
-  $variables['site_slogan']       = (theme_get_setting('features.slogan') ? filter_xss_admin($site_slogan) : '');
-
-  // Compile a list of classes that are going to be applied to the body element.
-  $variables['attributes']['class'][] = 'maintenance-page';
-  $variables['attributes']['class'][] = 'in-maintenance';
+  // @todo Rename the templates to page--maintenance + page--install.
+  template_preprocess_page($variables);
+
+  $page_object = $variables['page']['#page'];
+  $attributes = $page_object->getBodyAttributes();
+  $classes = $attributes['class'];
+  $classes[] = 'maintenance-page';
+  $classes[] = 'in-maintenance';
   if (isset($variables['db_is_active']) && !$variables['db_is_active']) {
-    $variables['attributes']['class'][] = 'db-offline';
-  }
-  if ($variables['layout'] == 'both') {
-    $variables['attributes']['class'][] = 'two-sidebars';
-  }
-  elseif ($variables['layout'] == 'none') {
-    $variables['attributes']['class'][] = 'no-sidebars';
-  }
-  else {
-    $variables['attributes']['class'][] = 'one-sidebar';
-    $variables['attributes']['class'][] = 'sidebar-' . $variables['layout'];
+    $classes[] = 'db-offline';
   }
+  $attributes['class'] = $classes;
 
-  $variables['head'] = drupal_get_html_head();
-
-  // While this code is used in the installer, the language module may not be
-  // enabled yet (even maybe no database set up yet), but an RTL language
-  // selected should result in RTL stylesheets loaded properly already.
-  $css = _drupal_add_css();
-  include_once DRUPAL_ROOT . '/core/modules/language/language.module';
-  // Wrapping drupal_get_css() and drupal_get_js() in an object so they can
-  // be called when printed.
-  $variables['styles'] = new RenderWrapper('drupal_get_css', array($css));
-  $variables['scripts'] = new RenderWrapper('drupal_get_js');
-
-  // Allow the page to define a title.
-  if (isset($variables['page']['#title'])) {
-    $variables['title'] = $variables['page']['#title'];
-  }
+  // @see system_page_build()
+  $attached = array(
+    '#attached' => array(
+      'library' => array(
+        'core/normalize',
+        'system/maintenance',
+      ),
+    ),
+  );
+  drupal_render($attached);
 }
 
 /**
@@ -2336,20 +2254,21 @@ function template_preprocess_maintenance_page(&$variables) {
  *
  * Default template: install-page.html.twig.
  *
- * The variables array generated here is a mirror of
- * template_preprocess_page(). This preprocessor will run its course when
- * theme_install_page() is invoked.
- *
  * @param array $variables
  *   An associative array containing:
  *   - content - An array of page content.
  *
  * @see template_preprocess_maintenance_page()
- *
  */
 function template_preprocess_install_page(&$variables) {
   template_preprocess_maintenance_page($variables);
-  $variables['attributes']['class'][] = 'install-page';
+
+  $page_object = $variables['page']['#page'];
+  $attributes = $page_object->getBodyAttributes();
+  $classes = $attributes['class'];
+  $classes[] = 'install-page';
+  $attributes['class'] = $classes;
+
   // Override the site name that is displayed on the page, since Drupal is
   // still in the process of being installed.
   $distribution_name = String::checkPlain(drupal_install_profile_distribution_name());
@@ -2464,11 +2383,11 @@ function drupal_common_theme() {
     ),
     // From theme.maintenance.inc.
     'maintenance_page' => array(
-      'variables' => array('content' => NULL, 'show_messages' => TRUE, 'page' => array()),
+      'render element' => 'page',
       'template' => 'maintenance-page',
     ),
     'install_page' => array(
-      'variables' => array('content' => NULL, 'show_messages' => TRUE, 'page' => array()),
+      'render element' => 'page',
       'template' => 'install-page',
     ),
     'task_list' => array(
diff --git a/core/includes/theme.maintenance.inc b/core/includes/theme.maintenance.inc
index d49338d..05e911f 100644
--- a/core/includes/theme.maintenance.inc
+++ b/core/includes/theme.maintenance.inc
@@ -30,6 +30,7 @@ function _drupal_maintenance_theme() {
   require_once __DIR__ . '/unicode.inc';
   require_once __DIR__ . '/file.inc';
   require_once __DIR__ . '/module.inc';
+  require_once __DIR__ . '/database.inc';
   Unicode::check();
 
   // Install and update pages are treated differently to prevent theming overrides.
@@ -42,13 +43,6 @@ function _drupal_maintenance_theme() {
     }
   }
   else {
-    // The bootstrap was not complete. So we are operating in a crippled
-    // environment, we need to bootstrap just enough to allow hook invocations
-    // to work. See _drupal_log_error().
-    if (!class_exists('Drupal\Core\Database\Database', FALSE)) {
-      require_once __DIR__ . '/database.inc';
-    }
-
     // Use the maintenance theme if specified, otherwise attempt to use the
     // default site theme.
     try {
diff --git a/core/includes/update.inc b/core/includes/update.inc
index 0bca244..58e47ba 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -14,6 +14,7 @@
 use Drupal\Core\Config\FileStorage;
 use Drupal\Core\Config\ConfigException;
 use Drupal\Core\DrupalKernel;
+use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Drupal\Core\Utility\Error;
 use Drupal\Component\Uuid\Uuid;
 use Drupal\Component\Utility\NestedArray;
@@ -151,15 +152,9 @@ function update_check_requirements($skip_warnings = FALSE) {
       '#theme' => 'status_report',
       '#requirements' => $requirements,
     );
-    $status_report = drupal_render($status);
-    $status_report .= 'Check the messages and <a href="' . check_url(drupal_requirements_url($severity)) . '">try again</a>.';
+    $status_report['#suffix'] = 'Check the messages and <a href="' . check_url(drupal_requirements_url($severity)) . '">try again</a>.';
     drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
-    $maintenance_page = array(
-      '#theme' => 'maintenance_page',
-      '#title' => 'Requirements problem',
-      '#content' => $status_report,
-    );
-    print drupal_render($maintenance_page);
+    print DefaultHtmlPageRenderer::renderPage($status_report, 'Requirements problem');
     exit();
   }
 }
diff --git a/core/lib/Drupal/Core/Controller/ExceptionController.php b/core/lib/Drupal/Core/Controller/ExceptionController.php
index d79567c..9302ab9 100644
--- a/core/lib/Drupal/Core/Controller/ExceptionController.php
+++ b/core/lib/Drupal/Core/Controller/ExceptionController.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Controller;
 
+use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Drupal\Core\Page\HtmlPageRendererInterface;
 use Drupal\Core\StringTranslation\TranslationInterface;
 use Symfony\Component\DependencyInjection\ContainerAwareInterface;
@@ -353,15 +354,8 @@ public function on500Html(FlattenException $exception, Request $request) {
       drupal_set_message($message, $class, TRUE);
     }
 
-    $page_content = array(
-      '#theme' => 'maintenance_page',
-      '#content' => t('The website has encountered an error. Please try again later.'),
-      '#page' => array(
-        '#title' => t('Error'),
-      ),
-    );
-
-    $output = drupal_render($page_content);
+    $content = t('The website has encountered an error. Please try again later.');
+    $output = DefaultHtmlPageRenderer::renderPage($content, t('Error'));
     $response = new Response($output);
     $response->setStatusCode(500, '500 Service unavailable (with message)');
 
diff --git a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
index 93bfb42..93501d0 100644
--- a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\Core\EventSubscriber;
 
+use Drupal\Component\Utility\String;
+use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\KernelEvents;
@@ -44,14 +46,10 @@ public function onKernelRequestMaintenance(GetResponseEvent $event) {
     if ($request->attributes->get('_maintenance') != MENU_SITE_ONLINE && !($response instanceof RedirectResponse)) {
       // Deliver the 503 page.
       drupal_maintenance_theme();
-      $maintenance_page = array(
-        '#theme' => 'maintenance_page',
-        '#title' => t('Site under maintenance'),
-        '#content' => filter_xss_admin(
-          t(\Drupal::config('system.maintenance')->get('message'), array('@site' => \Drupal::config('system.site')->get('name')))
-        ),
-      );
-      $content = drupal_render($maintenance_page);
+      $content = filter_xss_admin(String::format(\Drupal::config('system.maintenance')->get('message'), array(
+        '@site' => \Drupal::config('system.site')->get('name'),
+      )));
+      $content = DefaultHtmlPageRenderer::renderPage($content, t('Site under maintenance'));
       $response = new Response('Service unavailable', 503);
       $response->setContent($content);
       $event->setResponse($response);
diff --git a/core/lib/Drupal/Core/Page/DefaultHtmlPageRenderer.php b/core/lib/Drupal/Core/Page/DefaultHtmlPageRenderer.php
index 821d42d..4ce4ab2 100644
--- a/core/lib/Drupal/Core/Page/DefaultHtmlPageRenderer.php
+++ b/core/lib/Drupal/Core/Page/DefaultHtmlPageRenderer.php
@@ -23,4 +23,60 @@ public function render(HtmlPage $page) {
     return drupal_render($render);
   }
 
+  /**
+   * Renders a page using a custom page theme hook and optional region content.
+   *
+   * Temporary shim to facilitate modernization progress for special front
+   * contollers (install.php, update.php, authorize.php), maintenance mode, and
+   * the exception handler.
+   *
+   * Do NOT use this method in your code. This method will be removed as soon
+   * as architecturally possible.
+   *
+   * @param array|string $main
+   *   A render array or string containing the main page content.
+   * @param string $title
+   *   (optional) The page title.
+   * @param string $theme
+   *   (optional) The theme hook to use for rendering the page. The given value
+   *   is appended with '_page' at this point, since ultimately this parameter
+   *   will be converted into a theme template suggestion; i.e., #theme becomes
+   *   'page--$theme'. Defaults to 'maintenance'.
+   * @param array $regions
+   *   (optional) Additional region content to add to the page.
+   *
+   * @return string
+   *   The rendered HTML page.
+   *
+   * @internal
+   */
+  public static function renderPage($main, $title = '', $theme = 'maintenance', array $regions = array()) {
+    if (!is_array($main)) {
+      $main = array('#markup' => $main);
+    }
+    $page = new HtmlPage('', array(), $title);
+    $page_array = array(
+      '#type' => 'page',
+      // @todo Change this into "page__$theme" and rename templates into
+      //   page--maintenance and page--install.
+      '#theme' => $theme . '_page',
+      '#title' => $title,
+      'content' => array(
+        'system_main' => $main,
+      ),
+    );
+    $page_array += $regions;
+    $page_array += element_info('page');
+
+    // Allow modules and themes to alter the page render array.
+    \Drupal::moduleHandler()->alter('page', $page_array);
+
+    $page = \Drupal::service('html_fragment_renderer')->preparePage($page, $page_array);
+    $page->setBodyTop(drupal_render($page_array['page_top']));
+    $page->setBodyBottom(drupal_render($page_array['page_bottom']));
+    $page->setContent(drupal_render($page_array));
+
+    return \Drupal::service('html_page_renderer')->render($page);
+  }
+
 }
diff --git a/core/modules/system/templates/install-page.html.twig b/core/modules/system/templates/install-page.html.twig
index 031013e..ad1c04c 100644
--- a/core/modules/system/templates/install-page.html.twig
+++ b/core/modules/system/templates/install-page.html.twig
@@ -3,24 +3,14 @@
  * @file
  * Default theme implementation to display a Drupal installation page.
  *
- * All the available variables are mirrored in html.html.twig and
- * page.html.twig. Some may be blank but they are provided for consistency.
+ * All available variables are mirrored in page.html.twig.
+ * Some may be blank but they are provided for consistency.
  *
  * @see template_preprocess_install_page()
  *
  * @ingroup themeable
  */
 #}
-<!DOCTYPE html>
-<html{{ html_attributes }}>
-<head>
-  {{ head }}
-  <title>{{ head_title }}</title>
-  {{ styles }}
-  {{ scripts }}
-</head>
-<body class="{{ attributes.class }}">
-
   <div class="l-container">
 
     <header role="banner">
@@ -41,26 +31,25 @@
         <h1>{{ title }}</h1>
       {% endif %}
       {{ messages }}
-      {{ content }}
+      {{ page.content }}
     </main>
 
-    {% if sidebar_first %}
+    {% if page.sidebar_first %}
       <aside class="l-sidebar-first" role="complementary">
-        {{ sidebar_first }}
+        {{ page.sidebar_first }}
       </aside>{# /.l-sidebar-first #}
     {% endif %}
 
-    {% if sidebar_second %}
+    {% if page.sidebar_second %}
       <aside class="l-sidebar-second" role="complementary">
-        {{ sidebar_second }}
+        {{ page.sidebar_second }}
       </aside>{# /.l-sidebar-second #}
     {% endif %}
 
-    {% if footer %}
+    {% if page.footer %}
       <footer role="contentinfo">
-        {{ footer }}
+        {{ page.footer }}
       </footer>
     {% endif %}
 
-</body>
-</html>
+  </div>{# /.l-container #}
diff --git a/core/modules/system/templates/maintenance-page.html.twig b/core/modules/system/templates/maintenance-page.html.twig
index b5275c7..3b5a59e 100644
--- a/core/modules/system/templates/maintenance-page.html.twig
+++ b/core/modules/system/templates/maintenance-page.html.twig
@@ -3,7 +3,7 @@
  * @file
  * Default theme implementation to display a single Drupal page while offline.
  *
- * All of the available variables are mirrored in html.html.twig.
+ * All available variables are mirrored in page.html.twig.
  * Some may be blank but they are provided for consistency.
  *
  * @see template_preprocess_maintenance_page()
@@ -11,16 +11,6 @@
  * @ingroup themeable
  */
 #}
-<!DOCTYPE html>
-<html{{ html_attributes }}>
-<head>
-  {{ head }}
-  <title>{{ head_title }}</title>
-  {{ styles }}
-  {{ scripts }}
-</head>
-<body class="{{ attributes.class }}">
-
 <div class="l-container">
 
   <header role="banner">
@@ -53,7 +43,7 @@
 
     {{ messages }}
 
-    {{ content }}
+    {{ page.content }}
   </main>
 
   {% if page.sidebar_first %}
@@ -75,6 +65,3 @@
   {% endif %}
 
 </div>{# /.l-container #}
-
-</body>
-</html>
diff --git a/core/themes/bartik/bartik.theme b/core/themes/bartik/bartik.theme
index 642674c..176b798 100644
--- a/core/themes/bartik/bartik.theme
+++ b/core/themes/bartik/bartik.theme
@@ -94,7 +94,6 @@ function bartik_preprocess_maintenance_page(&$variables) {
   if (!$variables['db_is_active']) {
     $variables['site_name'] = '';
   }
-  $variables['styles'] = new RenderWrapper('drupal_get_css');
   // Normally we could attach libraries via hook_page_alter(), but when the
   // database is inactive it's not called so we add them here.
   $libraries = array(
@@ -104,6 +103,7 @@ function bartik_preprocess_maintenance_page(&$variables) {
       ),
     ),
   );
+  drupal_render($libraries);
 
   // Set the options that apply to both page and maintenance page.
   _bartik_process_page($variables);
diff --git a/core/themes/bartik/templates/maintenance-page.html.twig b/core/themes/bartik/templates/maintenance-page.html.twig
index b29cafa..604e176 100644
--- a/core/themes/bartik/templates/maintenance-page.html.twig
+++ b/core/themes/bartik/templates/maintenance-page.html.twig
@@ -3,27 +3,13 @@
  * @file
  * Bartik's theme implementation to display a single Drupal page while offline.
  *
- * All of the available variables are mirrored in html.html.twig.
+ * All available variables are mirrored in page.html.twig.
  *
  * @see template_preprocess_maintenance_page()
  *
  * @ingroup themeable
  */
  #}
-<!DOCTYPE html>
-<html{{ html_attributes }}>
-<head>
-  {{ head }}
-  <title>{{ head_title }}</title>
-  {{ styles }}
-  {{ scripts }}
-</head>
-<body class="{{ attributes.class }}"{{ attributes }}>
-
-  <a href="#main-content" class="visually-hidden focusable skip-link">
-    {{ 'Skip to main content'|t }}
-  </a>
-
   <div id="page-wrapper"><div id="page">
 
     <header id="header" role="banner"><div class="section clearfix">
@@ -49,7 +35,7 @@
       <main id="content" class="column" role="main"><section class="section">
         <a id="main-content"></a>
         {% if title %}<h1 class="title" id="page-title">{{ title }}</h1>{% endif %}
-        {{ content }}
+        {{ page.content }}
         {% if messages %}
           <div id="messages"><div class="section clearfix">
             {{ messages }}
@@ -59,6 +45,3 @@
     </div></div> <!-- /#main, /#main-wrapper -->
 
   </div></div> <!-- /#page, /#page-wrapper -->
-
-</body>
-</html>
diff --git a/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
index 6f5ce6b..9c47478 100644
--- a/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -269,8 +269,11 @@ function seven_element_info_alter(&$type) {
  * Implements hook_preprocess_install_page().
  */
 function seven_preprocess_install_page(&$variables) {
-  $variables['styles'] = new RenderWrapper('drupal_get_css');
-  $variables['scripts'] = new RenderWrapper('drupal_get_js');
+  $page_object = $variables['page']['#page'];
+  $attributes = $page_object->getHtmlAttributes();
+  $classes = $attributes['class'];
+  $classes[] = 'install-background';
+  $attributes['class'] = $classes;
 
   // Normally we could attach libraries via hook_page_alter(), but when the
   // database is inactive it's not called so we add them here.
diff --git a/core/themes/seven/templates/install-page.html.twig b/core/themes/seven/templates/install-page.html.twig
index 81ddece..e7903e6 100644
--- a/core/themes/seven/templates/install-page.html.twig
+++ b/core/themes/seven/templates/install-page.html.twig
@@ -3,8 +3,7 @@
  * @file
  * Seven theme implementation to display a Drupal installation page.
  *
- * All the available variables are mirrored in html.html.twig and
- * page.html.twig.
+ * All available variables are mirrored in page.html.twig.
  * Some may be blank but they are provided for consistency.
  *
  * @see template_preprocess_install_page()
@@ -12,16 +11,6 @@
  * @ingroup themeable
  */
 #}
-<!DOCTYPE html>
-<html{{ html_attributes }} class="install-background">
-<head>
-  {{ head }}
-  <title>{{ head_title }}</title>
-  {{ styles }}
-  {{ scripts }}
-</head>
-<body class="{{ attributes.class }}">
-
 <div class="l-container">
 
   <header role="banner">
@@ -37,9 +26,9 @@
     {% endif %}
   </header>
 
-  {% if sidebar_first %}
+  {% if page.sidebar_first %}
     <aside class="l-sidebar-first" role="complementary">
-      {{ sidebar_first }}
+      {{ page.sidebar_first }}
     </aside>{# /.l-sidebar-first #}
   {% endif %}
 
@@ -48,22 +37,19 @@
       <h1>{{ title }}</h1>
     {% endif %}
     {{ messages }}
-    {{ content }}
+    {{ page.content }}
   </main>
 
-  {% if sidebar_second %}
+  {% if page.sidebar_second %}
     <aside class="l-sidebar-second" role="complementary">
-      {{ sidebar_second }}
+      {{ page.sidebar_second }}
     </aside>{# /.l-sidebar-second #}
   {% endif %}
 
-  {% if footer %}
+  {% if page.page_bottom %}
     <footer role="contentinfo">
-      {{ footer }}
+      {{ page.page_bottom }}
     </footer>
   {% endif %}
 
 </div>{# /.l-container #}
-
-</body>
-</html>
diff --git a/core/themes/seven/templates/maintenance-page.html.twig b/core/themes/seven/templates/maintenance-page.html.twig
index dc691c1..2170d36 100644
--- a/core/themes/seven/templates/maintenance-page.html.twig
+++ b/core/themes/seven/templates/maintenance-page.html.twig
@@ -3,26 +3,14 @@
  * @file
  * Seven's theme implementation to display a single Drupal page while offline.
  *
- * All of the available variables are mirrored in html.html.twig.
+ * All available variables are mirrored in page.html.twig.
+ * Some may be blank but they are provided for consistency.
  *
  * @see template_preprocess_maintenance_page()
- * @see seven_preprocess_maintenance_page()
  *
  * @ingroup themeable
  */
 #}
-<!DOCTYPE html>
-<html{{ html_attributes }}>
-  <head>
-    <title>{{ head_title }}</title>
-    {{ head }}
-    {{ styles }}
-    {{ scripts }}
-  </head>
-  <body{{ attributes }}>
-
-  {{ page_top }}
-
   <header id="branding">
     <div class="branding__inner">
       {% if title %}<h1 class="page-title">{{ title }}</h1>{% endif %}
@@ -34,25 +22,22 @@
       {% if logo %}
         <img id="logo" src="{{ logo }}" alt="{{ site_name }}" />
       {% endif %}
-      {{ sidebar_first }}
+      {{ page.sidebar_first }}
     </div>
 
     <main id="content" class="clearfix">
       {% if messages %}
         <div id="console">{{ messages }}</div>
       {% endif %}
-      {% if help %}
+      {% if page.help %}
         <div id="help">
-          {{ help }}
+          {{ page.help }}
         </div>
       {% endif %}
-      {{ content }}
+      {{ page.content }}
     </main>
   </div>
 
   <footer role="contentinfo">
-    {{ page_bottom }}
+    {{ page.page_bottom }}
   </footer>
-
-  </body>
-</html>
diff --git a/core/themes/seven/templates/page.html.twig b/core/themes/seven/templates/page.html.twig
index 77dde87..2caeec2 100644
--- a/core/themes/seven/templates/page.html.twig
+++ b/core/themes/seven/templates/page.html.twig
@@ -50,13 +50,13 @@
  *   comment/reply/12345).
  *
  * Regions:
- * - page.header: Items for the header region.
+ * - page.page_top: Items for the header region.
  * - page.highlighted: Items for the highlighted content region.
  * - page.help: Dynamic help text, mostly for admin pages.
  * - page.content: The main content of the current page.
  * - page.sidebar_first: Items for the first sidebar.
  * - page.sidebar_second: Items for the second sidebar.
- * - page.footer: Items for the footer region.
+ * - page.page_bottom: Items for the footer region.
  *
  * @see template_preprocess_page()
  * @see seven_preprocess_page()
diff --git a/core/update.php b/core/update.php
index a2de6fc..61bba33 100644
--- a/core/update.php
+++ b/core/update.php
@@ -16,6 +16,7 @@
 
 use Drupal\Component\Utility\Settings;
 use Drupal\Core\DrupalKernel;
+use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Drupal\Core\Update\Form\UpdateScriptSelectionForm;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
@@ -457,18 +458,8 @@ function update_task_list($active = NULL) {
   }
   else {
     drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
-    $maintenance_page = array(
-      '#theme' => 'maintenance_page',
-      // $output has to be rendered here, because the maintenance page template
-      // is not wrapped into the html template, which means that any #attached
-      // libraries in $output will not be loaded, because the wrapping HTML has
-      // been printed already.
-      '#content' => drupal_render($output),
+    print DefaultHtmlPageRenderer::renderPage($output, $output['#title'], 'maintenance', array(
       '#show_messages' => !$progress_page,
-    );
-    if (isset($output['#title'])) {
-      $maintenance_page['#page']['#title'] = $output['#title'];
-    }
-    print drupal_render($maintenance_page);
+    ));
   }
 }