dominantSpeaker function
A comparator which sorts participants by the fact that they are the dominant speaker or not.
Implementation
int dominantSpeaker(CallParticipantState a, CallParticipantState b) {
if (a.isDominantSpeaker && !b.isDominantSpeaker) return -1;
if (!a.isDominantSpeaker && b.isDominantSpeaker) return 1;
return 0;
}