Set limit(-1) for findOperations when using first() in OperationIterable

Performance improvement for find().first() scenarios.
JAVA-1527
Looking at com.mongodb.DBCollection#findOne(com.mongodb.DBObject, com.mongodb.DBObject, com.mongodb.DBObject, com.mongodb.ReadPreference, long, java.util.concurrent.TimeUnit), it sets batchSize to -1 rather than limit.  Is there a difference?