/** Synchronization control for AbstractFutures. */
    private final Sync<V> sync = new Sync<V>();

    // The execution list to hold our executors.
    private final ExecutionList executionList = new ExecutionList();

    /** Constructor for use by subclasses. */
    protected OldAbstractFuture() {}

    /*
     * Improve the documentation of when InterruptedException is thrown. Our

    Object getImpl();
  }

  enum Impl {
    NEW {
      @Override
      ExecutionListWrapper newExecutionList() {
        return new ExecutionListWrapper() {
          final ExecutionList list = new ExecutionList();

          @Override
          public void add(Runnable runnable, Executor executor) {
            list.add(runnable, executor);
          }

          @Override