/usr/share/upstart/sessions/window-stack-bridge.conf is in hud 14.10+16.04.20160415-0ubuntu1.
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 | description "Window Stack Bridge"
start on started dbus
stop on desktop-end
exec /usr/lib/x86_64-linux-gnu/hud/window-stack-bridge
|