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

core/modules/history/js/mark-as-read.js

@@ -0,0 +1,23 @@
+/**
+ * @file
+ * Marks the nodes listed in drupalSettings.history.nodesToMarkAsRead as read.
+ *
+ * Uses the History module JavaScript API.
+ *
+ * @see Drupal.history
+ */
+
+(function (window, Drupal, drupalSettings) {
+
+  "use strict";
+
+  // When the window's "load" event is triggered, mark all enumerated nodes as
+  // read. This still allows for Drupal behaviors (which are triggered on the
+  // "DOMContentReady" event) to add "new" and "updated" indicators.
+  window.addEventListener('load', function () {
+    if (drupalSettings.history && drupalSettings.history.nodesToMarkAsRead) {
+      Object.keys(drupalSettings.history.nodesToMarkAsRead).forEach(Drupal.history.markAsRead);
+    }
+  });
+
+})(window, Drupal, drupalSettings);