I've noticed, that constant requests (every 20 seconds) are made to
.../admin/index.php?env=-index:m140--1-1-d-&front=1&admin=1&editing_mode=2&events[page-revision]=OnGetInfo url are made, while I was viewing a page in a "Content Mode" from Admin Console.
After a bit of investigation on that url I've found, that it's actually getting data about current page to show most recent revisions (in content editing toolbar) and if somebody has started editing same page in parallel. All that information is only useful if Page Content Revision Control is enabled.
I propose not to query such page information via ajax in case if we can't show it anywhere.