Bug 1635561 - Use RegionalPrefLocales rather than AppLocale in xpc_LocalizeRuntime; r=zbraniecki

Differential Revision: https://phabricator.services.mozilla.com/D98390

dom/tests/mochitest/chrome/test_intlUtils_getLocaleInfo.html

@@ -18,8 +18,7 @@ const localeService =
   Cc["@mozilla.org/intl/localeservice;1"].getService(Ci.mozILocaleService);
 const mozIntl = Cc["@mozilla.org/mozintl;1"].getService(Ci.mozIMozIntl);
 
-let rpLocale = localeService.negotiateLanguages(localeService.regionalPrefsLocales,
-                                                localeService.availableLocales)[0];
+let rpLocale = localeService.regionalPrefsLocales[0];
 
 let testData = [
   {

js/xpconnect/src/XPCLocale.cpp

@@ -133,11 +133,12 @@ bool xpc_LocalizeRuntime(JSRuntime* rt) {
   }
 
   // No pref has been found, so get the default locale from the
-  // application's locale.
-  nsAutoCString appLocaleStr;
-  LocaleService::GetInstance()->GetAppLocaleAsBCP47(appLocaleStr);
+  // regional prefs locales.
+  AutoTArray<nsCString, 10> rpLocales;
+  LocaleService::GetInstance()->GetRegionalPrefsLocales(rpLocales);
 
-  return JS_SetDefaultLocale(rt, appLocaleStr.get());
+  MOZ_ASSERT(rpLocales.Length() > 0);
+  return JS_SetDefaultLocale(rt, rpLocales[0].get());
 }
 
 void xpc_DelocalizeRuntime(JSRuntime* rt) {