function codePointsToString(code_points) {
    var s = '';
    for (var i = 0; i < code_points.length; ++i) {
      var cp = code_points[i];
      if (cp <= 0xFFFF) {
        s += String.fromCharCode(cp);
      } else {
        cp -= 0x10000;
        s += String.fromCharCode((cp >> 10) + 0xD800,
                                 (cp & 0x3FF) + 0xDC00);
      }
    }
    return s;
  }
@param {!Array.<number>} code_points Array of code points.
@return {string} string String of UTF-16 code units.