Synchronous XMLHttpRequest on the main thread is deprecated

[Ugoku]

Steps to reproduce:

• load OnlineJS in page
• OnlineJS calls the checkOnLine function, which in turn calls the checkOnLine function, which calls function checkConnectionWithRequest with the async parameter set to false.

The browser now gives the following warning: "Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check http://xhr.spec.whatwg.org/." (latest Opera/Chrome/Firefox).
Synchronous XHR has been deprecated since Firefox 30 (June 2014) and Chrome 40 (November 2014)

Although it seems that this will not be removed, it is still deprecated behaviour and should not be used.