AdjustablePolicy policy = new AdjustablePolicy(permissions);
      Policy.setPolicy(policy);

      try {
        r.run();
      } finally {
        policy.addPermission(new SecurityPermission("setPolicy"));
        Policy.setPolicy(savedPolicy);
      }
    }
  }

  /** Runs a runnable without any permissions. */
  public void runWithoutPermissions(Runnable r) {