src/main/java/io/reactivex/internal/util/QueueDrainHelper.java
public static void request(Subscription s, int prefetch) {
        s.request(prefetch < 0 ? Long.MAX_VALUE : prefetch);
    }
public static void request(Subscription s, int prefetch) {
        s.request(prefetch < 0 ? Long.MAX_VALUE : prefetch);
    }
Requests Long.MAX_VALUE if prefetch is negative or the exact
amount if prefetch is positive.
@param s the Subscription to request from
@param prefetch the prefetch value