Prepend [NSLocale currentLocale] for first locale on iOS to ensure countryCode exists. Allow language-only locales. (flutter#6995)

Author: GaryQian

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -748,18 +748,35 @@ - (void)onMemoryWarning:(NSNotification*)notification {
 
 - (void)onLocaleUpdated:(NSNotification*)notification {
   NSArray<NSString*>* preferredLocales = [NSLocale preferredLanguages];
-  NSMutableArray<NSString*>* data = [NSMutableArray new];
+  NSMutableArray<NSString*>* data = [[NSMutableArray new] autorelease];
+
+  // Force prepend the [NSLocale currentLocale] to the front of the list
+  // to ensure we are including the full default locale. preferredLocales
+  // is not guaranteed to include anything beyond the languageCode.
+  NSLocale* currentLocale = [NSLocale currentLocale];
+  NSString* languageCode = [currentLocale objectForKey:NSLocaleLanguageCode];
+  NSString* countryCode = [currentLocale objectForKey:NSLocaleCountryCode];
+  NSString* scriptCode = [currentLocale objectForKey:NSLocaleScriptCode];
+  NSString* variantCode = [currentLocale objectForKey:NSLocaleVariantCode];
+  if (languageCode) {
+    [data addObject:languageCode];
+    [data addObject:(countryCode ? countryCode : @"")];
+    [data addObject:(scriptCode ? scriptCode : @"")];
+    [data addObject:(variantCode ? variantCode : @"")];
+  }
+
+  // Add any secondary locales/languages to the list.
   for (NSString* localeID in preferredLocales) {
-    NSLocale* currentLocale = [[NSLocale alloc] initWithLocaleIdentifier:localeID];
+    NSLocale* currentLocale = [[[NSLocale alloc] initWithLocaleIdentifier:localeID] autorelease];
     NSString* languageCode = [currentLocale objectForKey:NSLocaleLanguageCode];
     NSString* countryCode = [currentLocale objectForKey:NSLocaleCountryCode];
     NSString* scriptCode = [currentLocale objectForKey:NSLocaleScriptCode];
     NSString* variantCode = [currentLocale objectForKey:NSLocaleVariantCode];
-    if (!languageCode || !countryCode) {
+    if (!languageCode) {
       continue;
     }
     [data addObject:languageCode];
-    [data addObject:countryCode];
+    [data addObject:(countryCode ? countryCode : @"")];
     [data addObject:(scriptCode ? scriptCode : @"")];
     [data addObject:(variantCode ? variantCode : @"")];
   }