code: public ChannelPromise doneAllocatingPromises() {
      if (!doneAllocating) {
        doneAllocating = true;
        if (successfulCount == expectedCount) {
          trySuccessInternal(null);
          return super.setSuccess(null);
        }
      }
      return this;
    }
docs: Signify that no more {@link #newPromise()} allocations will be made. The aggregation can not be
  successful until this method is called.
  
  @return {@code this} promise.