The `GetWindows` method gives access to the list of windows for each
application with some of their properties, so utilities such as dogtail
can pick the window of their choice to interfere with using the provided
window id.
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/326
(cherry picked from commit 0f45b438e2b956d3cf52622db875dedab45e49b9)
Add a D-Bus API that allows the API user to introspect the application
state of the shell. Currently the only exposed information is list of
running applications and which one is active (i.e. has focus).
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/326
(cherry picked from commit 10c68c6b952959d105c3126fc61f22a199e8e848)