added support for overriding locales

app/lib/features/geckoview/features/browser/domain/services/engine_settings_replication.dart

@@ -17,6 +17,7 @@
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
+import 'package:collection/collection.dart';
 import 'package:flutter/material.dart' show ThemeMode;
 import 'package:flutter_mozilla_components/flutter_mozilla_components.dart';
 import 'package:riverpod/riverpod.dart';
@@ -141,6 +142,18 @@ class EngineSettingsReplicationService
                   .read(preferenceFixatorProvider.notifier)
                   .register('pdfjs.disabled', !settings.enablePdfJs);
             }
+            if (!const DeepCollectionEquality.unordered().equals(
+              previous.value?.locales,
+              settings.locales,
+            )) {
+              // ignore: only_use_keep_alive_inside_keep_alive
+              await ref
+                  .read(preferenceFixatorProvider.notifier)
+                  .register(
+                    'intl.accept_languages',
+                    settings.locales.join(','),
+                  );
+            }
           } else {
             await _service.setDefaultSettings(settings);
 
@@ -149,6 +162,11 @@ class EngineSettingsReplicationService
                 .read(preferenceFixatorProvider.notifier)
                 .register('pdfjs.disabled', !settings.enablePdfJs);
 
+            // ignore: only_use_keep_alive_inside_keep_alive
+            await ref
+                .read(preferenceFixatorProvider.notifier)
+                .register('intl.accept_languages', settings.locales.join(','));
+
             initialSettingsSent = true;
           }
         }

app/lib/features/geckoview/features/browser/domain/services/engine_settings_replication.g.dart

@@ -44,7 +44,7 @@ final class EngineSettingsReplicationServiceProvider
 }
 
 String _$engineSettingsReplicationServiceHash() =>
-    r'd28cc58a94f45008a478bf52a9c40d61811b591d';
+    r'7583ebc8ca9c11377486ff5a3e763493dcdc903a';
 
 abstract class _$EngineSettingsReplicationService extends $Notifier<void> {
   void build();

app/lib/features/geckoview/features/preferences/data/repositories/preference_observer.dart

@@ -25,8 +25,6 @@ class PreferenceChangeListener extends _$PreferenceChangeListener {
 @Riverpod()
 class PreferenceFixator extends _$PreferenceFixator {
   Future<void> register(String name, Object value) async {
-    await GeckoPrefService().applyPrefs({name: value});
-
     state = {...state}
       ..update(
         name,
@@ -36,6 +34,8 @@ class PreferenceFixator extends _$PreferenceFixator {
           return value;
         },
       );
+
+    await GeckoPrefService().applyPrefs({name: value});
   }
 
   Future<void> unregister(String name) async {

app/lib/features/geckoview/features/preferences/data/repositories/preference_observer.g.dart

@@ -87,7 +87,7 @@ final class PreferenceFixatorProvider
   }
 }
 
-String _$preferenceFixatorHash() => r'dfa323859c660d3db74dba7297e2a33b758ed78a';
+String _$preferenceFixatorHash() => r'c76245d5c420e2e3f6c026f23c017c939b69ef59';
 
 abstract class _$PreferenceFixator extends $Notifier<Map<String, Object>> {
   Map<String, Object> build();