Comment 16 for bug 327863

I've been poking at this with debugging printfs, and indeed, despite the GfxScrollFrameInner object *thinking* it has hidden the horizontal scrollbar - that is, mHasHorizontalScrollbar is false and GetScrollPortSize() returns a rectangle with no space reserved for the horizontal scrollbar - the ScrollbarFrame for the horizontal scrollbar is visible and has a nonempty bounding rectangle. I'm able to reproduce this under xvfb *and* in a regular, but barebones, X session - just one xterm, a window manager, and ./dist/bin/firefox <tn's testcase>. It does *not* happen under a regular GNOME session, which continues to baffle me.

Anyway, this has moved my attention from the display list phase to the reflow phase, but I'm still trying to work out how that all works.