},
            directExecutor());
    for (int i = 0; i < 25_000; i++) {
      serializer.submit(Callables.<Void>returning(null), directExecutor()).cancel(true);
      unused = serializer.submit(Callables.<Void>returning(null), directExecutor());
    }
    ListenableFuture<Integer> stackDepthCheck =
        serializer.submit(
            new Callable<Integer>() {
              @Override
              public Integer call() {

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