cros: Remove the option to change locale from Settings during Demo Mode

It's unnecessary after the system tray button UI is added. Also the
locale list in Settings is not customized for Demo Mode.

Bug: 877749
Change-Id: I17c0ab8cab457a5a47416797677ce3b17d9b4b1b
Reviewed-on: https://chromium-review.googlesource.com/c/1334333
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608620}

chrome/browser/resources/settings/languages_page/languages_page.js

@@ -226,10 +226,8 @@ Polymer({
       menu.querySelector('#uiLanguageItem').hidden = true;
 
     // The UI language choice doesn't persist for guests.
-    if (loadTimeData.getBoolean('isGuest') &&
-        !loadTimeData.getBoolean('isDemoSession')) {
+    if (loadTimeData.getBoolean('isGuest'))
       menu.querySelector('#uiLanguageItem').hidden = true;
-    }
   },
 
   /**

chrome/browser/ui/webui/settings/languages_handler.cc

@@ -16,7 +16,6 @@
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/base/locale_util.h"
-#include "chrome/browser/chromeos/login/demo_mode/demo_session.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "components/user_manager/user_manager.h"
 #include "components/user_manager/user_type.h"
@@ -75,15 +74,13 @@ void LanguagesHandler::HandleSetProspectiveUILanguage(
   PrefService* prefs = g_browser_process->local_state();
   prefs->SetString(language::prefs::kApplicationLocale, language_code);
 #elif defined(OS_CHROMEOS)
-  // Secondary users and public session users (except for demo session users)
-  // cannot change the locale.
+  // Secondary users and public session users cannot change the locale.
   user_manager::UserManager* user_manager = user_manager::UserManager::Get();
   const user_manager::User* user =
       chromeos::ProfileHelper::Get()->GetUserByProfile(profile_);
   if (user &&
       user->GetAccountId() == user_manager->GetPrimaryUser()->GetAccountId() &&
-      (user->GetType() != user_manager::USER_TYPE_PUBLIC_ACCOUNT ||
-       chromeos::DemoSession::IsDeviceInDemoMode())) {
+      user->GetType() != user_manager::USER_TYPE_PUBLIC_ACCOUNT) {
     profile_->ChangeAppLocale(language_code,
                               Profile::APP_LOCALE_CHANGED_VIA_SETTINGS);
   }