You will need to install a user script manager extension to install this script.
This scripts allows you to bypass Page Visibility API.
For what purposes? Well, with it, you can play youtube video in background on Android web browsers which support userscript managers such as USI or Tampermonkey, even without Youtube Red subscription! Tested successfully on USI, Android Firefox!
Besides, If you want to bypass ads or countdowns which will pause counting if you switch tab, then this script is also suitable for you.
Or for other purposes that I still haven't thought up at the moment.