Synchronous XMLHttpRequest on the main thread is deprecated

[zhe1ka]

when i have several open tabs and when the connection is going to be disconnected in the tabs which aren't in focus I have the warning:

"Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/."

together with that i see the comment in the code that this behaviour is intended. The biggest problem that time-to-time it blocks the page (which is not in focus) completely for seconds or minutes. Can it be changed to async way of executing somehow?