This is used to request key focus on the close dialog whenever
a window that is frozen would receive key focus. Also, ensure
that the dialog gets focus when first shown if the window was
meant to receive input.
https://bugzilla.gnome.org/show_bug.cgi?id=762083
This is an interface that can be used to implement the "application
is not responding" dialog. One instance is created per window, which
is initially hidden, and can be shown/hidden on demand.
https://bugzilla.gnome.org/show_bug.cgi?id=711619