/usr/share/zsh/functions/Completion/X/ is in zsh-common 5.1.1-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/zsh/functions/Completion/X/_acroread
/usr/share/zsh/functions/Completion/X/_dcop
/usr/share/zsh/functions/Completion/X/_gnome-gv
/usr/share/zsh/functions/Completion/X/_gqview
/usr/share/zsh/functions/Completion/X/_gv
/usr/share/zsh/functions/Completion/X/_kfmclient
/usr/share/zsh/functions/Completion/X/_matlab
/usr/share/zsh/functions/Completion/X/_mozilla
/usr/share/zsh/functions/Completion/X/_mplayer
/usr/share/zsh/functions/Completion/X/_nautilus
/usr/share/zsh/functions/Completion/X/_nedit
/usr/share/zsh/functions/Completion/X/_netscape
/usr/share/zsh/functions/Completion/X/_okular
/usr/share/zsh/functions/Completion/X/_pdftk
/usr/share/zsh/functions/Completion/X/_qiv
/usr/share/zsh/functions/Completion/X/_rdesktop
/usr/share/zsh/functions/Completion/X/_setxkbmap
/usr/share/zsh/functions/Completion/X/_urxvt
/usr/share/zsh/functions/Completion/X/_vnc
/usr/share/zsh/functions/Completion/X/_x_arguments
/usr/share/zsh/functions/Completion/X/_x_borderwidth
/usr/share/zsh/functions/Completion/X/_x_color
/usr/share/zsh/functions/Completion/X/_x_colormapid
/usr/share/zsh/functions/Completion/X/_x_cursor
/usr/share/zsh/functions/Completion/X/_x_display
/usr/share/zsh/functions/Completion/X/_x_extension
/usr/share/zsh/functions/Completion/X/_x_font
/usr/share/zsh/functions/Completion/X/_x_geometry
/usr/share/zsh/functions/Completion/X/_x_keysym
/usr/share/zsh/functions/Completion/X/_x_locale
/usr/share/zsh/functions/Completion/X/_x_modifier
/usr/share/zsh/functions/Completion/X/_x_name
/usr/share/zsh/functions/Completion/X/_x_resource
/usr/share/zsh/functions/Completion/X/_x_selection_timeout
/usr/share/zsh/functions/Completion/X/_x_title
/usr/share/zsh/functions/Completion/X/_x_utils
/usr/share/zsh/functions/Completion/X/_x_visual
/usr/share/zsh/functions/Completion/X/_x_window
/usr/share/zsh/functions/Completion/X/_xauth
/usr/share/zsh/functions/Completion/X/_xautolock
/usr/share/zsh/functions/Completion/X/_xclip
/usr/share/zsh/functions/Completion/X/_xdvi
/usr/share/zsh/functions/Completion/X/_xfig
/usr/share/zsh/functions/Completion/X/_xft_fonts
/usr/share/zsh/functions/Completion/X/_xloadimage
/usr/share/zsh/functions/Completion/X/_xmodmap
/usr/share/zsh/functions/Completion/X/_xournal
/usr/share/zsh/functions/Completion/X/_xpdf
/usr/share/zsh/functions/Completion/X/_xrandr
/usr/share/zsh/functions/Completion/X/_xscreensaver
/usr/share/zsh/functions/Completion/X/_xset
/usr/share/zsh/functions/Completion/X/_xt_arguments
/usr/share/zsh/functions/Completion/X/_xt_session_id
/usr/share/zsh/functions/Completion/X/_xterm
/usr/share/zsh/functions/Completion/X/_xv
/usr/share/zsh/functions/Completion/X/_xwit