Currently gnome-control-center could crash whenever a connection
test is interrupted by the disposal of the Printers panel.
Searching in the g-c-c shell for any query that could match the
Printers panel would instantiate the CcPrintersPanel class. Since
we perform a connection test to the printing server as soon as this
object is created, a fast disposal of the panel (by choosing another
search result) would cause the whole application to crash.
https://bugzilla.gnome.org/show_bug.cgi?id=792753
PpCups object represents local CUPS server. It contains
asynchronous method for getting printers installed on
the server. It is an asynchronous version of cupsGetDests().
(#683229)
