Update to Drupal 8.0.6. For more information, see https://www.drupal.org/drupal-8.0.6-release-notes

core/lib/Drupal/Core/Render/Element/HtmlTag.php

@@ -28,7 +28,7 @@ use Drupal\Core\Template\Attribute;
  * Usage example:
  * @code
  * $build['hello'] = [
- *   '#type' => 'html_tag'
+ *   '#type' => 'html_tag',
  *   '#tag' => 'p',
  *   '#value' => $this->t('Hello World'),
  * ];

core/lib/Drupal/Core/Render/Element/Tableselect.php

@@ -259,6 +259,7 @@ class Tableselect extends Table {
               '#return_value' => $key,
               '#default_value' => isset($value[$key]) ? $key : NULL,
               '#attributes' => $element['#attributes'],
+              '#ajax' => isset($element['#ajax']) ? $element['#ajax'] : NULL,
             );
           }
           else {

core/lib/Drupal/Core/Render/Element/VerticalTabs.php

@@ -136,7 +136,7 @@ class VerticalTabs extends RenderElement {
     $element[$name . '__active_tab'] = array(
       '#type' => 'hidden',
       '#default_value' => $element['#default_tab'],
-      '#attributes' => array('class' => array('vertical-tabs-active-tab')),
+      '#attributes' => array('class' => array('vertical-tabs__active-tab')),
     );
     // Clean up the active tab value so it's not accidentally stored in
     // settings forms.

core/lib/Drupal/Core/Render/theme.api.php

@@ -324,8 +324,11 @@
  *   namespace Element, and generally extend the
  *   \Drupal\Core\Render\Element\FormElement base class.
  * See the @link plugin_api Plugin API topic @endlink for general information
- * on plugins, and look for classes with the RenderElement or FormElement
- * annotation to discover what render elements are available.
+ * on plugins. You can search for classes with the RenderElement or FormElement
+ * annotation to discover what render elements are available. API reference
+ * sites (such as https://api.drupal.org) generate lists of all existing
+ * elements from these classes. Look for the Elements link in the API Navigation
+ * block.
  *
  * Modules can define render elements by defining an element plugin.
  *