service.awaitTermination(terminationTimeout, timeUnit);
                  } catch (InterruptedException ignored) {
                    // We're shutting down anyway, so just ignore.
                  }
                }
              }));
    }

    @VisibleForTesting
    void addShutdownHook(Thread hook) {
      Runtime.getRuntime().addShutdownHook(hook);
    }
  }

  }

  // TODO: Re-enable this test after moving to new serialization format in ImmutableMap.
  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  @SuppressWarnings("unchecked")
  public void ignore_testSerializationNoDuplication_regularImmutableMap() throws Exception {
    // Tests that serializing a map, its keySet, and values only writes the underlying data once.

    Object[] entries = new Object[2000];