From the manual - Browser object..
Triggered when the page's visibility changes, or when a mobile app is going in to the background or foreground. When invisible or in the background the app is suspended: all events stop running and all audio is muted
So it seems the app automatically stops all events..
So it's impossible to keep the app running..
What you could do is use the system time plugin, to detect at what time the app was suspended and use it again on resumed to make the events happen that would have happened during the suspended time..