bug#42112: 27.0.91; whitespace-empty face not extended beyond EOL

["Basil L. Contovounesios" <contovob@tcd.ie>]

Severity: minor

Steps to reproduce:

0. emacs -Q
1. M-x whitespace-mode RET
2. M-<

In Emacs 26, line 3 is highlighted with the whitespace-empty face all
the way to the right fringe.

In Emacs 27, only the first two columns of line 3 are highlighted with
the whitespace-empty face.

Is this TRT?  Should whitespace-empty get an ':extend t' attribute or
inherit from some other face which already has that?

Thanks,

-- 
Basil

In GNU Emacs 27.0.91 (build 23, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2020-06-28 built on thunk
Repository revision: cce00bef0313bc42beee8096d9312313889dc92d
Repository branch: emacs-27
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Debian GNU/Linux bullseye/sid

Configured using:
 'configure 'CC=ccache gcc' 'CFLAGS=-O0 -g3 -ggdb -gdwarf-4'
 --config-cache --prefix=/home/blc/.local --program-suffix=27
 --enable-checking=yes,glyphs --enable-check-lisp-object-type
 --with-x-toolkit=lucid --with-file-notification=yes --with-x'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF
XFT ZLIB TOOLKIT_SCROLL_BARS LUCID X11 XDBE XIM MODULES THREADS
LIBSYSTEMD JSON PDUMPER LCMS2 GMP