/usr/ is in libgdm-dev 3.18.3-0ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/pkgconfig/
/usr/lib/x86_64-linux-gnu/pkgconfig/gdm.pc
/usr/include/
/usr/include/gdm/
/usr/include/gdm/gdm-sessions.h
/usr/include/gdm/gdm-user-switching.h
/usr/include/gdm/gdm-client-glue.h
/usr/include/gdm/gdm-client.h
/usr/share/
/usr/share/gir-1.0/
/usr/share/gir-1.0/Gdm-1.0.gir
/usr/share/doc/
/usr/share/doc/libgdm-dev/
/usr/share/doc/libgdm-dev/copyright
/usr/lib/x86_64-linux-gnu/libgdm.so
/usr/share/doc/libgdm-dev/NEWS.gz
/usr/share/doc/libgdm-dev/AUTHORS
/usr/share/doc/libgdm-dev/changelog.Debian.gz
/usr/share/doc/libgdm-dev/README