/usr/share/gnome-session/sessions/ubuntu.session is in ubuntu-session 3.9.90-0ubuntu12.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | [GNOME Session]
Name=Ubuntu
RequiredComponents=unity-settings-daemon;compiz;
DesktopName=Unity
|