/usr/share/gdm/greeter/applications/gnome-shell-wayland.desktop is in gdm3 3.18.3-0ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | [Desktop Entry]
Type=Application
Name=GNOME Shell
Comment=Window management and compositing
Exec=gnome-shell --mode=gdm --wayland --display-server
X-GNOME-Autostart-Phase=DisplayServer
X-GNOME-Autostart-Notify=true
X-GNOME-AutoRestart=true
X-Ubuntu-Gettext-Domain=gdm
|