This was almost certainly my fault, but as I look at the implementation of Sets.cartesianProduct, I think its `contains` method made the assumption that `ImmutableSet.asList().indexOf` was O(1), which is no longer the case for Android.  It should probably get a specific `contains` implementation that actually is O(sets), not O(sets*setSize).
}
    @Override
    public E pollLast() {
      return forward.pollFirst();
    }
    @Override
    public NavigableSet<E> descendingSet() {
      return forward;
    }
    @Override
    public Iterator<E> descendingIterator() {
      return forward.iterator();
    }
    @Override
    public NavigableSet<E> subSet(
        E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
      return forward.subSet(toElement, toInclusive, fromElement, fromInclusive).descendingSet();
    }
    @Override
    public SortedSet<E> subSet(E fromElement, E toElement) {
      return standardSubSet(fromElement, toElement);
    }
    @Override
    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
      return forward.tailSet(toElement, inclusive).descendingSet();
    }
    @Override
    public SortedSet<E> headSet(E toElement) {
      return standardHeadSet(toElement);
    }