Set AppLocale global preference on network screen.

chrome/browser/ui/webui/chromeos/login/network_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/network_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/network_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/network_screen_handler.cc
index 74a731d154e8c8de8a7ca2765fc601826eb36eeb..bd67a5a4c170c1d3770fe176071e58397c079395 100644
--- a/chrome/browser/ui/webui/chromeos/login/network_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/network_screen_handler.cc
@@ -312,6 +312,12 @@ void NetworkScreenHandler::OnLanguageChangedCallback(
 
   self->ReloadLocalizedContent();
 
+  // We still do not have device owner, so owner settings are not applied.
+  // But Guest session can be started before owner is created, so we need to
+  // save locale settings directly here.
+  g_browser_process->local_state()->SetString(prefs::kApplicationLocale,
+                                              self->selected_language_code_);
+
   AccessibilityManager::Get()->OnLocaleChanged();
 }