Revert "Implement ResolveLocale in C++."

This reverts commit 1a225459.

Reason for revert: Makes GC stress unhappy: https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux%20-%20gc%20stress/18325 and blocks the roll

Original change's description:
> Implement ResolveLocale in C++.
> 
> Bug: v8:8065, v8:5751
> Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
> Change-Id: Id9dc16455d63b7c436126c21758d64fae0ec8de9
> Reviewed-on: https://chromium-review.googlesource.com/1211402
> Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
> Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#55925}

TBR=bstell@chromium.org,gsathya@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: v8:8065, v8:5751
Change-Id: I4d71adb31ffd5ab0d2ae42c0255d0a05edbaad29
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/1226646Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Michael Hablich <hablich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55932}

src/contexts.h

@@ -96,6 +96,7 @@ enum ContextLookupFlags {
   V(REFERENCE_ERROR_FUNCTION_INDEX, JSFunction, reference_error_function) \
   V(CACHED_OR_NEW_SERVICE_LOCALE_FUNCTION_INDEX, JSFunction,              \
     cached_or_new_service)                                                \
+  V(RESOLVE_LOCALE_FUNCTION_INDEX, JSFunction, resolve_locale)            \
   V(SET_ADD_INDEX, JSFunction, set_add)                                   \
   V(SET_DELETE_INDEX, JSFunction, set_delete)                             \
   V(SET_HAS_INDEX, JSFunction, set_has)                                   \

src/objects/intl-objects.h

@@ -89,13 +89,6 @@ class Intl {
   static bool RemoveLocaleScriptTag(const std::string& icu_locale,
                                     std::string* locale_less_script);
 
-  struct ResolvedLocale {
-    std::string locale;  // The bcp47 locale to use.
-    std::string unicode_extensions;
-    std::map<std::string, std::string> extensions;
-    std::string locale_with_extensions;
-  };
-
   // The ResolveLocale abstract operation compares a BCP 47 language
   // priority list requestedLocales against the locales in
   // availableLocales and determines the best available language to
@@ -105,15 +98,14 @@ class Intl {
   //
   // #ecma402/sec-partitiondatetimepattern
   //
-  // Returns an object with two properties:
+  // Returns a JSObject with two properties:
   //   (1) locale
   //   (2) extension
-  V8_WARN_UNUSED_RESULT static Maybe<ResolvedLocale*> ResolveLocale(
-      Isolate* isolate, const char* service,
-      const std::set<std::string>& available_locales,
-      const std::vector<std::string>& requested_locales,
-      const std::set<std::string>& relevant_extension_keys,
-      Handle<JSReceiver> options);
+  //
+  // To access either, use JSObject::GetDataProperty.
+  V8_WARN_UNUSED_RESULT static MaybeHandle<JSObject> ResolveLocale(
+      Isolate* isolate, const char* service, Handle<Object> requestedLocales,
+      Handle<Object> options);
 
   // This currently calls out to the JavaScript implementation of
   // CanonicalizeLocaleList.

src/objects/js-break-iterator.cc

@@ -28,9 +28,6 @@ MaybeHandle<JSV8BreakIterator> JSV8BreakIterator::InitializeV8BreakIterator(
     Isolate* isolate, Handle<JSV8BreakIterator> break_iterator_holder,
     Handle<Object> locales, Handle<Object> options_obj) {
   Factory* factory = isolate->factory();
-  Maybe<std::vector<std::string>> requested_locales =
-      Intl::CanonicalizeLocaleList(isolate, locales, false);
-  MAYBE_RETURN(requested_locales, MaybeHandle<JSV8BreakIterator>());
 
   Handle<JSReceiver> options;
   if (options_obj->IsUndefined(isolate)) {
@@ -43,18 +40,15 @@ MaybeHandle<JSV8BreakIterator> JSV8BreakIterator::InitializeV8BreakIterator(
   }
 
   // Extract locale string
-  const std::set<std::string> relevant_extension_keys;
-  std::set<std::string> available_locales =
-      Intl::GetAvailableLocales(IcuService::kListFormatter);
-  Maybe<Intl::ResolvedLocale*> maybe_resolved_locale = Intl::ResolveLocale(
-      isolate, "breakiterator", available_locales, requested_locales.FromJust(),
-      relevant_extension_keys, options);
-  MAYBE_RETURN(maybe_resolved_locale, MaybeHandle<JSV8BreakIterator>());
-  std::unique_ptr<Intl::ResolvedLocale> r(maybe_resolved_locale.FromJust());
-  CHECK_NOT_NULL(r.get());
-
-  Handle<String> locale =
-      isolate->factory()->NewStringFromAsciiChecked(r.get()->locale.c_str());
+  Handle<JSObject> r;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, r,
+      Intl::ResolveLocale(isolate, "breakiterator", locales, options),
+      JSV8BreakIterator);
+  Handle<Object> locale_obj =
+      JSObject::GetDataProperty(r, factory->locale_string());
+  CHECK(locale_obj->IsString());
+  Handle<String> locale = Handle<String>::cast(locale_obj);
 
   // Extract type from options
   std::unique_ptr<char[]> type_str = nullptr;

src/objects/js-collator.cc

@@ -221,9 +221,10 @@ MaybeHandle<JSCollator> JSCollator::InitializeCollator(
     Isolate* isolate, Handle<JSCollator> collator, Handle<Object> locales,
     Handle<Object> options_obj) {
   // 1. Let requestedLocales be ? CanonicalizeLocaleList(locales).
-  Maybe<std::vector<std::string>> requested_locales =
-      Intl::CanonicalizeLocaleList(isolate, locales, false);
-  MAYBE_RETURN(requested_locales, MaybeHandle<JSCollator>());
+  Handle<JSObject> requested_locales;
+  ASSIGN_RETURN_ON_EXCEPTION(isolate, requested_locales,
+                             Intl::CanonicalizeLocaleListJS(isolate, locales),
+                             JSCollator);
 
   // 2. If options is undefined, then
   if (options_obj->IsUndefined(isolate)) {
@@ -256,7 +257,10 @@ MaybeHandle<JSCollator> JSCollator::InitializeCollator(
     }
   }
 
-  // Steps 9 and 10 are done as part of the Intl::ResolveLocale call below.
+  // TODO(gsathya): This is currently done as part of the
+  // Intl::ResolveLocale call below. Fix this once resolveLocale is
+  // changed to not do the lookup.
+  //
   // 9. Let matcher be ? GetOption(options, "localeMatcher", "string",
   // « "lookup", "best fit" », "best fit").
   // 10. Set opt.[[localeMatcher]] to matcher.
@@ -312,20 +316,25 @@ MaybeHandle<JSCollator> JSCollator::InitializeCollator(
   // requestedLocales, opt, %Collator%.[[RelevantExtensionKeys]],
   // localeData).
   // 18. Set collator.[[Locale]] to r.[[locale]].
-  std::set<std::string> available_locales =
-      Intl::GetAvailableLocales(IcuService::kCollator);
-  Maybe<Intl::ResolvedLocale*> maybe_resolved_locale = Intl::ResolveLocale(
-      isolate, "collator", available_locales, requested_locales.FromJust(),
-      relevant_extension_keys, options);
-  MAYBE_RETURN(maybe_resolved_locale, MaybeHandle<JSCollator>());
-  std::unique_ptr<Intl::ResolvedLocale> r(maybe_resolved_locale.FromJust());
-  CHECK_NOT_NULL(r.get());
-
-  std::string locale_with_extension = r.get()->locale_with_extensions;
-  Handle<String> locale = isolate->factory()->NewStringFromAsciiChecked(
-      locale_with_extension.c_str());
-
-  icu::Locale icu_locale = Intl::CreateICULocale(isolate, locale);
+  Handle<JSObject> r;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, r,
+      Intl::ResolveLocale(isolate, "collator", requested_locales, options),
+      JSCollator);
+
+  Handle<String> locale_with_extension_str =
+      isolate->factory()->NewStringFromStaticChars("localeWithExtension");
+  Handle<Object> locale_with_extension_obj =
+      JSObject::GetDataProperty(r, locale_with_extension_str);
+
+  // The locale_with_extension has to be a string. Either a user
+  // provided canonicalized string or the default locale.
+  CHECK(locale_with_extension_obj->IsString());
+  Handle<String> locale_with_extension =
+      Handle<String>::cast(locale_with_extension_obj);
+
+  icu::Locale icu_locale =
+      Intl::CreateICULocale(isolate, locale_with_extension);
   DCHECK(!icu_locale.isBogus());
 
   std::map<std::string, std::string> extensions =

src/objects/js-date-time-format.cc

@@ -775,12 +775,7 @@ enum FormatMatcherOption { kBestFit, kBasic };
 // ecma402/#sec-initializedatetimeformat
 MaybeHandle<JSDateTimeFormat> JSDateTimeFormat::Initialize(
     Isolate* isolate, Handle<JSDateTimeFormat> date_time_format,
-    Handle<Object> locales, Handle<Object> input_options) {
-  // 1. Let requestedLocales be ? CanonicalizeLocaleList(locales).
-  Maybe<std::vector<std::string>> requested_locales =
-      Intl::CanonicalizeLocaleList(isolate, locales, false);
-  MAYBE_RETURN(requested_locales, MaybeHandle<JSDateTimeFormat>());
-
+    Handle<Object> requested_locales, Handle<Object> input_options) {
   // 2. Let options be ? ToDateTimeOptions(options, "any", "date").
   Handle<JSObject> options;
   ASSIGN_RETURN_ON_EXCEPTION(
@@ -789,26 +784,29 @@ MaybeHandle<JSDateTimeFormat> JSDateTimeFormat::Initialize(
           isolate, input_options, RequiredOption::kAny, DefaultsOption::kDate),
       JSDateTimeFormat);
 
-  const std::set<std::string> relevant_extension_keys{"ca", "nu", "hc"};
-
   // 11. Let r be ResolveLocale( %DateTimeFormat%.[[AvailableLocales]],
   //     requestedLocales, opt, %DateTimeFormat%.[[RelevantExtensionKeys]],
   //     localeData).
   const char* kService = "Intl.DateTimeFormat";
-  std::set<std::string> available_locales =
-      Intl::GetAvailableLocales(IcuService::kRelativeDateTimeFormatter);
-  Maybe<Intl::ResolvedLocale*> maybe_resolved_locale = Intl::ResolveLocale(
-      isolate, "datetimeformat", available_locales,
-      requested_locales.FromJust(), relevant_extension_keys, options);
-  MAYBE_RETURN(maybe_resolved_locale, MaybeHandle<JSDateTimeFormat>());
-  std::unique_ptr<Intl::ResolvedLocale> r(maybe_resolved_locale.FromJust());
-  CHECK_NOT_NULL(r.get());
-
-  std::string locale_with_extension = r.get()->locale_with_extensions;
-  Handle<String> locale = isolate->factory()->NewStringFromAsciiChecked(
-      locale_with_extension.c_str());
-
-  icu::Locale icu_locale = Intl::CreateICULocale(isolate, locale);
+  Handle<JSObject> r;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, r,
+      Intl::ResolveLocale(isolate, "dateformat", requested_locales, options),
+      JSDateTimeFormat);
+
+  Handle<String> locale_with_extension_str =
+      isolate->factory()->NewStringFromStaticChars("localeWithExtension");
+  Handle<Object> locale_with_extension_obj =
+      JSObject::GetDataProperty(r, locale_with_extension_str);
+
+  // The locale_with_extension has to be a string. Either a user
+  // provided canonicalized string or the default locale.
+  CHECK(locale_with_extension_obj->IsString());
+  Handle<String> locale_with_extension =
+      Handle<String>::cast(locale_with_extension_obj);
+
+  icu::Locale icu_locale =
+      Intl::CreateICULocale(isolate, locale_with_extension);
   DCHECK(!icu_locale.isBogus());
 
   // We implement only best fit algorithm, but still need to check

src/objects/js-list-format.cc

@@ -122,10 +122,7 @@ JSListFormat::Type get_type(const char* str) {
 MaybeHandle<JSListFormat> JSListFormat::InitializeListFormat(
     Isolate* isolate, Handle<JSListFormat> list_format_holder,
     Handle<Object> input_locales, Handle<Object> input_options) {
-  Maybe<std::vector<std::string>> requested_locales =
-      Intl::CanonicalizeLocaleList(isolate, input_locales, false);
-  MAYBE_RETURN(requested_locales, MaybeHandle<JSListFormat>());
-
+  Factory* factory = isolate->factory();
   list_format_holder->set_flags(0);
 
   Handle<JSReceiver> options;
@@ -173,23 +170,23 @@ MaybeHandle<JSListFormat> JSListFormat::InitializeListFormat(
 
   // 10. Let r be ResolveLocale(%ListFormat%.[[AvailableLocales]],
   // requestedLocales, opt, undefined, localeData).
-  const std::set<std::string> relevant_extension_keys;
-  std::set<std::string> available_locales =
-      Intl::GetAvailableLocales(IcuService::kListFormatter);
-  Maybe<Intl::ResolvedLocale*> maybe_resolved_locale = Intl::ResolveLocale(
-      isolate, "listformatter", available_locales, requested_locales.FromJust(),
-      relevant_extension_keys, options);
-  MAYBE_RETURN(maybe_resolved_locale, MaybeHandle<JSListFormat>());
-  std::unique_ptr<Intl::ResolvedLocale> r(maybe_resolved_locale.FromJust());
-  CHECK_NOT_NULL(r.get());
-
-  Handle<String> locale =
-      isolate->factory()->NewStringFromAsciiChecked(r.get()->locale.c_str());
+  Handle<JSObject> r;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, r,
+      Intl::ResolveLocale(isolate, "listformat", input_locales, options),
+      JSListFormat);
+
+  Handle<Object> locale_obj =
+      JSObject::GetDataProperty(r, factory->locale_string());
+  Handle<String> locale;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, locale, Object::ToString(isolate, locale_obj), JSListFormat);
 
   // 18. Set listFormat.[[Locale]] to the value of r.[[Locale]].
   list_format_holder->set_locale(*locale);
 
-  icu::Locale icu_locale(r.get()->locale.c_str());
+  std::unique_ptr<char[]> locale_name = locale->ToCString();
+  icu::Locale icu_locale(locale_name.get());
   UErrorCode status = U_ZERO_ERROR;
   icu::ListFormatter* formatter = icu::ListFormatter::createInstance(
       icu_locale, GetIcuStyleString(style_enum, type_enum), status);

src/objects/js-number-format.cc

@@ -189,9 +189,10 @@ MaybeHandle<JSNumberFormat> JSNumberFormat::Initialize(
   number_format->set_flags(0);
   Factory* factory = isolate->factory();
   // 1. Let requestedLocales be ? CanonicalizeLocaleList(locales).
-  Maybe<std::vector<std::string>> requested_locales =
-      Intl::CanonicalizeLocaleList(isolate, locales, false);
-  MAYBE_RETURN(requested_locales, MaybeHandle<JSNumberFormat>());
+  Handle<JSObject> requested_locales;
+  ASSIGN_RETURN_ON_EXCEPTION(isolate, requested_locales,
+                             Intl::CanonicalizeLocaleListJS(isolate, locales),
+                             JSNumberFormat);
 
   // 2. If options is undefined, then
   if (options_obj->IsUndefined(isolate)) {
@@ -211,8 +212,6 @@ MaybeHandle<JSNumberFormat> JSNumberFormat::Initialize(
 
   // 4. Let opt be a new Record.
   //
-  // Steps 5 and 6 are currently done as part of the
-  // Intl::ResolveLocale call below.
   // 5. Let matcher be ? GetOption(options, "localeMatcher", "string", «
   // "lookup", "best fit" », "best fit").
   //
@@ -226,26 +225,29 @@ MaybeHandle<JSNumberFormat> JSNumberFormat::Initialize(
   //
   // 9. Set numberFormat.[[Locale]] to r.[[locale]].
 
-  std::set<std::string> available_locales =
-      Intl::GetAvailableLocales(IcuService::kNumberFormat);
-  // 13.3.3 Internal slots
-  // https://tc39.github.io/ecma402/#sec-intl.numberformat-internal-slots
-  const std::set<std::string> relevant_extension_keys{"nu"};
-  Maybe<Intl::ResolvedLocale*> maybe_resolved_locale = Intl::ResolveLocale(
-      isolate, "numberformat", available_locales, requested_locales.FromJust(),
-      relevant_extension_keys, options);
-  MAYBE_RETURN(maybe_resolved_locale, MaybeHandle<JSNumberFormat>());
-  std::unique_ptr<Intl::ResolvedLocale> r(maybe_resolved_locale.FromJust());
-  CHECK_NOT_NULL(r.get());
-
-  std::string locale_with_extension = r.get()->locale_with_extensions;
-  Handle<String> locale = isolate->factory()->NewStringFromAsciiChecked(
-      locale_with_extension.c_str());
-
-  icu::Locale icu_locale = Intl::CreateICULocale(isolate, locale);
-  number_format->set_locale(*locale);
+  Handle<JSObject> r;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, r,
+      Intl::ResolveLocale(isolate, "numberformat", requested_locales, options),
+      JSNumberFormat);
+
+  Handle<String> locale_with_extension_str =
+      isolate->factory()->NewStringFromStaticChars("localeWithExtension");
+  Handle<Object> locale_with_extension_obj =
+      JSObject::GetDataProperty(r, locale_with_extension_str);
+
+  // The locale_with_extension has to be a string. Either a user
+  // provided canonicalized string or the default locale.
+  CHECK(locale_with_extension_obj->IsString());
+  Handle<String> locale_with_extension =
+      Handle<String>::cast(locale_with_extension_obj);
+
+  icu::Locale icu_locale =
+      Intl::CreateICULocale(isolate, locale_with_extension);
+  number_format->set_locale(*locale_with_extension);
   DCHECK(!icu_locale.isBogus());
 
+  std::set<std::string> relevant_extension_keys{"nu"};
   std::map<std::string, std::string> extensions =
       Intl::LookupUnicodeExtensions(icu_locale, relevant_extension_keys);
 

src/objects/js-plural-rules.cc

@@ -89,9 +89,12 @@ MaybeHandle<JSPluralRules> JSPluralRules::InitializePluralRules(
     Isolate* isolate, Handle<JSPluralRules> plural_rules,
     Handle<Object> locales, Handle<Object> options_obj) {
   // 1. Let requestedLocales be ? CanonicalizeLocaleList(locales).
-  Maybe<std::vector<std::string>> requested_locales =
-      Intl::CanonicalizeLocaleList(isolate, locales, false);
-  MAYBE_RETURN(requested_locales, MaybeHandle<JSPluralRules>());
+  // TODO(jkummerow): Port ResolveLocale, then use the C++ version of
+  // CanonicalizeLocaleList here.
+  Handle<JSObject> requested_locales;
+  ASSIGN_RETURN_ON_EXCEPTION(isolate, requested_locales,
+                             Intl::CanonicalizeLocaleListJS(isolate, locales),
+                             JSPluralRules);
 
   // 2. If options is undefined, then
   if (options_obj->IsUndefined(isolate)) {
@@ -109,8 +112,10 @@ MaybeHandle<JSPluralRules> JSPluralRules::InitializePluralRules(
   // At this point, options_obj can either be a JSObject or a JSProxy only.
   Handle<JSReceiver> options = Handle<JSReceiver>::cast(options_obj);
 
-  // Steps 5 and 6 are currently done as part of the
-  // Intl::ResolveLocale call below.
+  // TODO(gsathya): This is currently done as part of the
+  // Intl::ResolveLocale call below. Fix this once resolveLocale is
+  // changed to not do the lookup.
+  //
   // 5. Let matcher be ? GetOption(options, "localeMatcher", "string",
   // « "lookup", "best fit" », "best fit").
   // 6. Set opt.[[localeMatcher]] to matcher.
@@ -141,21 +146,19 @@ MaybeHandle<JSPluralRules> JSPluralRules::InitializePluralRules(
   // 11. Let r be ResolveLocale(%PluralRules%.[[AvailableLocales]],
   // requestedLocales, opt, %PluralRules%.[[RelevantExtensionKeys]],
   // localeData).
-  std::set<std::string> available_locales =
-      Intl::GetAvailableLocales(IcuService::kPluralRules);
-  // 13.3.3 Internal slots
-  // https://tc39.github.io/ecma402/#sec-intl.pluralrules-internal-slots
-  // The value of the [[RelevantExtensionKeys]] internal slot is [].
-  const std::set<std::string> relevant_extension_keys;
-  Maybe<Intl::ResolvedLocale*> maybe_resolved_locale = Intl::ResolveLocale(
-      isolate, "pluralrules", available_locales, requested_locales.FromJust(),
-      relevant_extension_keys, options);
-  MAYBE_RETURN(maybe_resolved_locale, MaybeHandle<JSPluralRules>());
-  std::unique_ptr<Intl::ResolvedLocale> r(maybe_resolved_locale.FromJust());
-  CHECK_NOT_NULL(r.get());
-
-  Handle<String> locale =
-      isolate->factory()->NewStringFromAsciiChecked(r.get()->locale.c_str());
+  Handle<JSObject> r;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, r,
+      Intl::ResolveLocale(isolate, "pluralrules", requested_locales, options),
+      JSPluralRules);
+
+  Handle<String> locale_str = isolate->factory()->locale_string();
+  Handle<Object> locale_obj = JSObject::GetDataProperty(r, locale_str);
+
+  // The locale has to be a string. Either a user provided
+  // canonicalized string or the default locale.
+  CHECK(locale_obj->IsString());
+  Handle<String> locale = Handle<String>::cast(locale_obj);
 
   // 12. Set pluralRules.[[Locale]] to the value of r.[[locale]].
   plural_rules->set_locale(*locale);

src/objects/js-relative-time-format.cc

@@ -59,10 +59,7 @@ MaybeHandle<JSRelativeTimeFormat>
 JSRelativeTimeFormat::InitializeRelativeTimeFormat(
     Isolate* isolate, Handle<JSRelativeTimeFormat> relative_time_format_holder,
     Handle<Object> input_locales, Handle<Object> input_options) {
-  Maybe<std::vector<std::string>> requested_locales =
-      Intl::CanonicalizeLocaleList(isolate, input_locales, false);
-  MAYBE_RETURN(requested_locales, MaybeHandle<JSRelativeTimeFormat>());
-
+  Factory* factory = isolate->factory();
   relative_time_format_holder->set_flags(0);
   // 4. If options is undefined, then
   Handle<JSReceiver> options;
@@ -81,20 +78,17 @@ JSRelativeTimeFormat::InitializeRelativeTimeFormat(
   //                            requestedLocales, opt,
   //                            %RelativeTimeFormat%.[[RelevantExtensionKeys]],
   //                            localeData).
-  std::set<std::string> available_locales =
-      Intl::GetAvailableLocales(IcuService::kRelativeDateTimeFormatter);
-  // 13.3.3 Internal slots
-  // The value of the [[RelevantExtensionKeys]] internal slot is [].
-  const std::set<std::string> relevant_extension_keys;
-  Maybe<Intl::ResolvedLocale*> maybe_resolved_locale = Intl::ResolveLocale(
-      isolate, "relativetimeformat", available_locales,
-      requested_locales.FromJust(), relevant_extension_keys, options);
-  MAYBE_RETURN(maybe_resolved_locale, MaybeHandle<JSRelativeTimeFormat>());
-  std::unique_ptr<Intl::ResolvedLocale> r(maybe_resolved_locale.FromJust());
-  CHECK_NOT_NULL(r.get());
-
-  Handle<String> locale =
-      isolate->factory()->NewStringFromAsciiChecked(r.get()->locale.c_str());
+  Handle<JSObject> r;
+  ASSIGN_RETURN_ON_EXCEPTION(isolate, r,
+                             Intl::ResolveLocale(isolate, "relativetimeformat",
+                                                 input_locales, options),
+                             JSRelativeTimeFormat);
+  Handle<Object> locale_obj =
+      JSObject::GetDataProperty(r, factory->locale_string());
+  Handle<String> locale;
+  ASSIGN_RETURN_ON_EXCEPTION(isolate, locale,
+                             Object::ToString(isolate, locale_obj),
+                             JSRelativeTimeFormat);
 
   // 11. Let locale be r.[[Locale]].
   // 12. Set relativeTimeFormat.[[Locale]] to locale.