/usr/share/gnome-shell/extensions/ is in gnome-shell-extension-appindicator 18.04.1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/appIndicator.js
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/dbusMenu.js
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/extension.js
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/iconCache.js
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/indicatorStatusIcon.js
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/interfaces-xml/
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/interfaces-xml/DBusMenu.xml
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/interfaces-xml/Properties.xml
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/interfaces-xml/StatusNotifierItem.xml
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/interfaces-xml/StatusNotifierWatcher.xml
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/interfaces.js
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/metadata.json
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/statusNotifierWatcher.js
/usr/share/gnome-shell/extensions/ubuntu-appindicators@ubuntu.com/util.js