Further to Lars' invitation[1] in bug#25096, I attach two patches.  The
first updates eww and shr faces to use the newer (DISPLAY . PLIST) face
spec syntax, and the second sets the :version tag of shr faces.

[1] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25096#48

P.S. I noticed that the docstrings of all three shr faces begin with the
     term "font".  Is this deviation from the term "face" intentional?

Thanks,

-- 
Basil

In GNU Emacs 27.0.50 (build 5, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2018-04-17 built on thunk
Repository revision: 62a075b01678c6a6f5d2a69c9ea6904a3927f1b4
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Debian GNU/Linux buster/sid