recordNames = record =>
  // https://github.com/endojs/endo/pull/1260#discussion_r1003657244
  // compares two ways of reverse sorting, and shows that `.sort().reverse()`
  // is currently faster on Moddable XS, while the other way,
  // `.sort(reverseComparator)`, is faster on v8. We currently care more about
  // XS performance, so we reverse sort using `.sort().reverse()`.
  harden(/** @type {string[]} */ (ownKeys(record)).sort().reverse())
Assuming that `record` is a CopyRecord, we have only
string-named own properties. `recordNames` returns those name *reverse*
sorted, because that's how records are compared, encoded, and sorted.

@template {Passable} T
@param {CopyRecord<T>} record
@returns {string[]}