Comment # 19 on bug 843086 from Felix Miata

In 42.3 just updated on host p5bse, which has none of the special configuration
of comment 16 or 18 and Adwaita selected for GTK(2), Firefox ESR rv52 from
mozilla.org (GTK3), Firefox ESR from mozilla.org 45.9 (GTK2) and SeaMonkey rv52
(contributed by frg 2.49.1x) specially built with GTK2 for testing email fixes
since 2.46 release all have no scrollbar icons.

As to FF 52 and other GTK3 apps a new bug is probably needed due to lack of
support in KControl.