function copyExistingProperties(src, dst) {
  Object.keys(dst).forEach(function (key) {
    if (dst.hasOwnProperty(key) && src.hasOwnProperty(key)) {
      /* eslint no-prototype-builtins: 0 */
      dst[key] = src[key];
    }
  });
}
Copies properties from source to dest only if a matching key is in dest

@param {Object.<string, ?>} src the source
@param {Object.<string, ?>} dst the dest
@private