[CentOS] Scroll bar arrows missing and behaviour change

>
> I agree that issue with the scroll bar jumping all over is really
> annoying!
> It is actually a feature of Gnome and GTK.  It can be changed by editing a
> file:
>
> ~/.config/gtk-3.0/settings.ini
>
> [Settings]
> gtk-primary-button-warps-slider=0
>
>
I also find this behavior annoying.  I tried adding this settings file (it
didn't exist) and logging out and back in, but Firefox still jumps do the
absolute location on the scrollbar.  I'm on CentOS 7.3.