/usr/share/applications/signon-ui.desktop is in signon-ui-x11 0.17+16.04.20151125-0ubuntu1.
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 7 8 9 10 11 | [Desktop Entry]
Encoding=UTF-8
Version=1.0
Name=Account authentication
Comment=Login to online accounts
Exec=/usr/bin/signon-ui
Icon=
Type=Application
Terminal=false
NoDisplay=true
X-Ubuntu-Gettext-Domain=signon-ui
|