if (seenExceptions == null) {
      seenExceptions = newHashSet();
      addInitialException(seenExceptions);
    }
    return seenExceptions;
  }

  abstract void addInitialException(Set<Throwable> seen);

  final int decrementRemainingAndGet() {
    return --remaining;
  }

  final void clearSeenExceptions() {
    seenExceptions = null;
  }

       */
      seenExceptionsLocal = requireNonNull(seenExceptions);
    }
    return seenExceptionsLocal;
  }

  /** Populates {@code seen} with the exception that was passed to {@code setException}. */
  abstract void addInitialException(Set<Throwable> seen);

  final int decrementRemainingAndGet() {
    return ATOMIC_HELPER.decrementAndGetRemainingCount(this);
  }

  final void clearSeenExceptions() {