I remember I used to "use" Xnest with scrollbars, and I thought the scrollbars came from Xnest. Of course, I never really did have much use for it; just cool to run a different desktop environment in there.

Maybe what I'm really remembering is running an Xnest in FVWM2, which can toss scrollbars on any window. It was some years ago last I messed with it, so that's a likely explanation. Sorry about the false lead.