font-lock and face names

[Dieter Wilhelm]

Hi

In a major mode I'm using for the font-lock-keywords mostly faces
which are defined in font-lock.el.  Now I'd like to use other faces
which are shown with list-faces-display, e. g. scroll-bar.  But I
can't use these without making a variable known (defvar scroll-bar
'scroll-bar).  Is there a reason why these defvars aren't already done
in their respective source files and why is this variable defintion
necessary at all in addition to the defface definition?
-- 
    Best wishes

    H. Dieter Wilhelm
    Darmstadt, Germany