As far as I can tell, this has always been unused. My hunch is that this was supposed to mimick the `MultiplexExternalSemaSource::AddSource` API which `SemaSourceWithPriorities` is based on.
As far as I can tell, this has always been unused. My hunch is that this was supposed to mimick the `MultiplexExternalSemaSource::AddSource` API which `SemaSourceWithPriorities` is based on.