/etc/apparmor.d/abstractions/X is in apparmor 2.7.102-0ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 | # vim:syntax=apparmor
# ------------------------------------------------------------------
#
#    Copyright (C) 2002-2009 Novell/SUSE
#    Copyright (C) 2009-2011 Canonical Ltd.
#
#    This program is free software; you can redistribute it and/or
#    modify it under the terms of version 2 of the GNU General Public
#    License published by the Free Software Foundation.
#
# ------------------------------------------------------------------
  # .ICEauthority files required for X authentication, per user
  @{HOME}/.ICEauthority r,
  # .Xauthority files required for X connections, per user
  @{HOME}/.Xauthority           r,
  owner /{,var/}run/gdm/*/database r,
  owner /{,var/}run/lightdm/authority/[0-9]* r,
  # the unix socket to use to connect to the display
  /tmp/.X11-unix/*           w,
  /usr/include/X11/               r,
  /usr/include/X11/**             r,
  # The X tree changes and is large -- grant read access to the whole thing
  /usr/X11R6/**                   r,
  /usr/share/X11/                 r,
  /usr/share/X11/**               r,
  /usr/X11R6/**.so*               mr,
  # DRI
  /usr/lib{,32,64}/dri/**         mr,
  /usr/lib/@{multiarch}/dri/**    mr,
  /dev/dri/**                     rw,
  /etc/drirc                      r,
  owner @{HOME}/.drirc            r,
  # mouse themes
  /etc/X11/cursors/               r,
  /etc/X11/cursors/**             r,
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