When I upgraded from Natty to Oneiric and then immediately to Precise, for some reason the overlay scrollbars stopped appearing. They were enabled and worked just fine in Natty, and are still enabled in theory. I've purged and reinstalled these packages: overlay-scrollbar, liboverlay-scrollbar-0.2-0, and liboverlay-scrollbar3-0.2-0. That did nothing. I also tried using both Ubuntu Tweak and Unsettings, but both showed that overlay scrollbars were turned on (and turning the settings off and back on again did nothing either).

Any ideas how to get them back? Thanks!

Edit: I just read that some people disable them by adding a line in ~/.xprofile or /etc/X11/Xsession.d/99disable-overlay-scrollbars, but those files don't exist.