I figured it out. [From the documentation][1]: **`(0W8`**.

[I found the following somewhat related answer on another SE site][2], to explain why I use a double-indent (i.e. `(0W8` instead of `(0W4`) for continuation lines (i.e. Google and Oracle style guides encourage it).

    WN    When in unclosed parentheses and N is non-zero and either
          using "(0" or "u0", respectively and the unclosed parentheses is
          the last non-white character in its line and it is not the
          closing parentheses, indent the following line N characters
          relative to the outer context (i.e. start of the line or the
          next unclosed parentheses).  (default: 0).

            cino=(0                    cino=(0,W4
              a_long_line(              a_long_line(
                          argument,         argument,
                          argument);        argument);
              a_short_line(argument,    a_short_line(argument,
                           argument);                argument);

  [1]: http://vimdoc.sourceforge.net/htmldoc/indent.html#cinoptions-values
  [2]: https://stackoverflow.com/a/699313/1022889