Investigate "Always show scrollbars" option

There's an option in Firefox called "Always show scrollbars". The pref is widget.gtk.overlay-scrollbars.enabled.

It may be worth to investigate if it affects fingerprintability, and probably lock it to ensure the same value for all users.

Also may be worth to investigate widget.gtk.hide-pointer-while-typing.enabled (hidden pref, no UI available for it) in terms of fingerprintability.