bug#15427: 24.3.50; `customize-face' in Customize, show `Background' attribute using background

[Drew Adams <drew.adams@oracle.com>]

> > emacs -Q
> > M-x customize-face lazy-highlight
> >
> > Attribute `Background' has its own `sample', which shows the color.
> > But it shows the color as a foreground (text).  Show it as the
> > background, instead.
> >
> > This is independent of the overall `sample' for the face as a whole.
> > It's just more helpful to show the background color choice as a
> > background.
> 
> There's a whole bunch of things that can have a colour when customising
> a face -- like stipple background/foreground, overline, etc.  I don't
> know whether it makes sense to special-case just the (main) background
> colour...  but perhaps that does make sense, because it's a pretty
> common thing to customise.  And showing the colour as a background
> colour would give a more correct impressions.
> 
> But might be confusing if that one thing behaved differently than the
> rest.
> 
> Anybody have an opinion here?

It's _not_ about one thing behaving differently.

We show an overline, underline, foreground, etc.
attribute using the foreground, because they are,
well, in the foreground.

Attribute background is not.  Attribute background
should, well, show the color sample as background,
not as foreground.  (I would think that this is
obviously TRT to do.)