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).
* set is serializable.
   *
   * @return a new, empty thread-safe {@code Set}
   * @since 15.0
   */
  public static <E> Set<E> newConcurrentHashSet() {
    return Collections.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
  }
  /**
   * Creates a thread-safe set backed by a hash map and containing the given elements. The set is
   * backed by a {@link ConcurrentHashMap} instance, and thus carries the same concurrency
   * guarantees.
   *
   * <p>Unlike {@code HashSet}, this class does NOT allow {@code null} to be used as an element. The
   * set is serializable.
   *
   * @param elements the elements that the set should contain
   * @return a new thread-safe set containing those elements (minus duplicates)
   * @throws NullPointerException if {@code elements} or any of its contents is null
   * @since 15.0
   */
  public static <E> Set<E> newConcurrentHashSet(Iterable<? extends E> elements) {
    Set<E> set = newConcurrentHashSet();
    Iterables.addAll(set, elements);
    return set;
  }
  
  /**
   * Creates a <i>mutable</i>, empty {@code LinkedHashSet} instance.
   *