Manually setting overlays, instead of choosing a specific mode, is still
supported through SystemUiMode.manual, allowing developers to pass the same
list of overlays as before.

Migration guide

Code before migration:

SystemChrome

setEnabledSystemUIOverlays

(<

SystemUiOverlay

>[

SystemUiOverlay

top

SystemUiOverlay

bottom

]);

Code after migration:

SystemChrome

setEnabledSystemUIMode

SystemUiMode

manual

overlays:

SystemUiOverlay

>[

SystemUiOverlay

top

SystemUiOverlay

bottom

],