Revert inadvertent normative change

05f7a11 (part of #2670)
inadvertently made an observable change. This restores the previous
observable semantics.

Thanks to Anba for spotting this.

Closes: #2721

polyfill/lib/ecmascript.mjs

@@ -5201,6 +5201,7 @@ export function AddDurationToOrSubtractDurationFromPlainYearMonth(operation, yea
   }
   let { years, months, weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds } = duration;
   ({ days } = BalanceTimeDuration(days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds, 'day'));
+  options = GetOptionsObject(options);
   const sign = DurationSign(years, months, weeks, days, 0, 0, 0, 0, 0, 0);
 
   const calendarRec = new CalendarMethodRecord(GetSlot(yearMonth, CALENDAR), [
@@ -5240,7 +5241,6 @@ export function AddDurationToOrSubtractDurationFromPlainYearMonth(operation, yea
     startDate = CalendarDateFromFields(calendarRec, fieldsCopy);
   }
   const durationToAdd = new Duration(years, months, weeks, days, 0, 0, 0, 0, 0, 0);
-  options = GetOptionsObject(options);
   const optionsCopy = SnapshotOwnProperties(options, null);
   const addedDate = AddDate(calendarRec, startDate, durationToAdd, options);
   const addedDateFields = PrepareTemporalFields(addedDate, fieldNames, []);

spec/plainyearmonth.html

@@ -676,6 +676,7 @@ <h1>
         1. If _operation_ is ~subtract~, then
           1. Set _duration_ to ! CreateNegatedTemporalDuration(_duration_).
         1. Let _balanceResult_ be ? BalanceTimeDuration(_duration_.[[Days]], _duration_.[[Hours]], _duration_.[[Minutes]], _duration_.[[Seconds]], _duration_.[[Milliseconds]], _duration_.[[Microseconds]], _duration_.[[Nanoseconds]], *"day"*).
+        1. Set _options_ to ? GetOptionsObject(_options_).
         1. Let _sign_ be ! DurationSign(_duration_.[[Years]], _duration_.[[Months]], _duration_.[[Weeks]], _balanceResult_.[[Days]], 0, 0, 0, 0, 0, 0).
         1. Let _calendarRec_ be ? CreateCalendarMethodsRecord(_yearMonth_.[[Calendar]], « ~dateAdd~, ~dateFromFields~, ~day~, ~fields~, ~yearMonthFromFields~ »).
         1. Let _fieldNames_ be ? CalendarFields(_calendarRec_, « *"monthCode"*, *"year"* »).
@@ -694,7 +695,6 @@ <h1>
         1. Else,
           1. Let _date_ be _intermediateDate_.
         1. Let _durationToAdd_ be ! CreateTemporalDuration(_duration_.[[Years]], _duration_.[[Months]], _duration_.[[Weeks]], _balanceResult_.[[Days]], 0, 0, 0, 0, 0, 0).
-        1. Set _options_ to ? GetOptionsObject(_options_).
         1. Let _optionsCopy_ be ? SnapshotOwnProperties(_options_, *null*).
         1. Let _addedDate_ be ? AddDate(_calendarRec_, _date_, _durationToAdd_, _options_).
         1. Let _addedDateFields_ be ? PrepareTemporalFields(_addedDate_, _fieldNames_, «»).