According to an article at https://developers.google.com/web/updates/2017/03/background_tabs
Google Chrome will slow down Javascript from tabs that you have backgrounded. Sometimes I wait for games in a background tab. I've seen a game suddenly connect to a player instantly when returning to the tab, so this suggests that the page may be getting starved for Javascript execution in a background tab.
Is it confirmed that this is happening for the game, and is there a good workaround?