public synchronized void addProgressListener(QProgressListener<I> listener) {
		if (progressListener == null) {
			progressListener = listener;
		}
		else {
			progressListener = new ChainedProgressListener<>(progressListener, listener);
		}
	}
Adds a progress listener for this queue.  All the progress and messages reported by a
QWorker will be routed to these listener.

@param listener the listener for receiving progress and message notifications.
Ghidra/Framework/Generic/src/main/java/generic/concurrent/ConcurrentQ.java