[ermine][l10n] Sets the system locale based on Flutter values, too.

This is required for the time being for the intl subsystem to be
able to vary locales.

Bug: 41657
Change-Id: Ib8bb128d00b33bb6e0bcc486d307f7739507c1f9
diff --git a/session_shells/ermine/shell/lib/src/widgets/app.dart b/session_shells/ermine/shell/lib/src/widgets/app.dart
index 5bab193..c1763de 100644
--- a/session_shells/ermine/shell/lib/src/widgets/app.dart
+++ b/session_shells/ermine/shell/lib/src/widgets/app.dart
@@ -9,6 +9,7 @@
 import 'package:internationalization/supported_locales.dart'
     as supported_locales;
 import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:intl/intl.dart';
 
 import '../models/app_model.dart';
 import '../utils/styles.dart';
@@ -29,6 +30,9 @@
         stream: model.localeStream,
         builder: (context, snapshot) {
           final locale = snapshot.data;
+          // Needed to set the locale for anything that depends on the Intl
+          // package.
+          Intl.defaultLocale = locale.toString();
           return MaterialApp(
             debugShowCheckedModeBanner: false,
             theme: ErmineStyle.kErmineTheme,