Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/action/action.views_execution.inc

@@ -0,0 +1,24 @@
+<?php
+
+/**
+ * @file
+ * Provides views runtime hooks for action.module.
+ */
+
+use Drupal\Component\Utility\SafeMarkup;
+
+/**
+ * Implements hook_views_form_substitutions().
+ */
+function action_views_form_substitutions() {
+  // Views SafeMarkup::checkPlain()s the column label, so we need to match that.
+  $select_all_placeholder = SafeMarkup::checkPlain('<!--action-bulk-form-select-all-->');
+  $select_all = array(
+    '#type' => 'checkbox',
+    '#default_value' => FALSE,
+    '#attributes' => array('class' => array('action-table-select-all')),
+  );
+  return array(
+    $select_all_placeholder => drupal_render($select_all),
+  );
+}