This allows for
XRemoteContentProviderAcceptor::addRemoteContentProvider
to be implemented in a layz fashion (remember the remote content
providers, but do not register them right away), which can increase
performance in certain situations. But it is not required that an
implementation of XRemoteContentProviderAcceptor uses this
lazy strategy (and thus also implements this interface).
Returns
the broker at which the remote content providers have been registered.