325.08/325.15 change breaks Firefox layer acceleration

This change in the 325 series has caused a problem with Firefox layers acceleration:
Generate a BadMatch error when applications attempt to create GLX pixmaps using glXCreatePixmap() or glXCreateGLXPixmapWithConfigSGIX() and the pixmap’s depth doesn’t match that of the specified GLXFBConfig.

See the bug report here: https://bugzilla.mozilla.org/show_bug.cgi?id=896287