This queue allows a ThreadPoolExecutor to steal jobs from another ThreadPoolExecutor. This queue
also acts as the factory for creating the PriorityBlockingQueue to be used in the steal-from
ThreadPoolExecutor. The behavior of this queue is the same as a normal PriorityBlockingQueue
except the take/poll(long,TimeUnit) methods would also check whether there are jobs in the
steal-from queue if this q ueue is empty. Note the workers in ThreadPoolExecutor must be
pre-started so that they can steal job from the other queue, otherwise the worker will only be
started after there are jobs submitted to main queue.