media player services are not registered as org.mpris.MediaPlayer2 just
use a service name that starts with that. We need to watch all services
and then filter.
BUG: 352529
Reviewed-by: Albert Vaca
We used to have the following warning: "Connecting to deprecated signal
QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)"
Port away from it as recommended in Qt documentation.
REVIEW: 123637