function indexPointerFor(code_point, index) {
    var pointer = index.indexOf(code_point);
    return pointer === -1 ? null : pointer;
  }
@param {number} code_point The |code point| to search for.
@param {!Array.<?number>} index The |index| to search within.
@return {?number} The first pointer corresponding to |code point| in
    |index|, or null if |code point| is not in |index|.