protected static boolean addSnapRange(long lower, long upper, MutableLifeSet spanSet,
			List<Lifespan> ordered) {
		if (spanSet.contains(lower)) {
			return false;
		}
		Lifespan range = Lifespan.span(lower, upper);
		spanSet.add(range);
		ordered.add(range);
		return true;
	}
NB. Because occlusion.occluded can be expensive, we should only keep the lock long enough
to copy the spans.
Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/trace/database/DBTraceTimeViewport.java