Update to Drupal 8.0.2. For more information, see https://www.drupal.org/drupal-8.0.2-release-notes

core/modules/tracker/tracker.module

@@ -135,8 +135,8 @@ function tracker_cron() {
 /**
  * Access callback: Determines access permission for a user's own account.
  *
- * @param int $account
- *   The account ID to check.
+ * @param \Drupal\Core\Session\AccountInterface $account
+ *   The user account to track.
  *
  * @return bool
  *   TRUE if a user is accessing tracking info for their own account and

core/modules/tracker/tracker.pages.inc

@@ -14,6 +14,9 @@ use Drupal\node\Entity\Node;
  * Queries the database for info, adds RDFa info if applicable, and generates
  * the render array that will be used to render the page.
  *
+ * @param \Drupal\user\UserInterface $account
+ *   (optional) The user account to track.
+ *
  * @return array
  *   A renderable array.
  *