/usr/share/ is in gnome-session-flashback 1:3.8.0-1ubuntu11.
This file is owned by root:root, with mode 0o755.
..
/usr/share/gnome-session/
/usr/share/gnome-session/sessions/
/usr/share/gnome-session/sessions/gnome-flashback-compiz.session
/usr/share/gnome-session/sessions/gnome-flashback.session
/usr/share/xsessions/
/usr/share/xsessions/gnome-fallback.desktop
/usr/share/xsessions/gnome-fallback-compiz.desktop
/usr/share/doc/
/usr/share/doc/gnome-session-flashback/
/usr/share/doc/gnome-session-flashback/README
/usr/share/doc/gnome-session-flashback/NEWS.gz
/usr/share/doc/gnome-session-flashback/AUTHORS
/usr/share/doc/gnome-session-flashback/copyright
/usr/share/doc/gnome-session-flashback/changelog.Debian.gz
/usr/share/applications/
/usr/share/applications/gnome-flashback-services.desktop
/usr/share/applications/gnome-wm.desktop
/usr/share/gnome-session/sessions/gnome-fallback-compiz.session
/usr/share/gnome-session/sessions/gnome-fallback.session