cros: Enable changing locale from system tray in demo mode

Show a locale feature button in the unified system tray in demo
mode. The UI is implemented in //ash/system, but the data should come
from //chrome.

The mock is in go/CrosDemoLanguage. No additional spec is needed: the
UI is consistent with other buttons in the system tray. The change is
approved by UI review.

Bug: 877749
Change-Id: I23a88584845e432b7762aeac03ab86d659cca07c
Reviewed-on: https://chromium-review.googlesource.com/c/1321775
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Stefan Kuhne <skuhne@chromium.org>
Reviewed-by: Oliver Chang <ochang@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608557}

ash/BUILD.gn

@@ -707,8 +707,14 @@ component("ash") {
     "system/keyboard_brightness/unified_keyboard_brightness_slider_controller.cc",
     "system/keyboard_brightness/unified_keyboard_brightness_slider_controller.h",
     "system/keyboard_brightness_control_delegate.h",
+    "system/locale/locale_detailed_view.cc",
+    "system/locale/locale_detailed_view.h",
+    "system/locale/locale_feature_pod_controller.cc",
+    "system/locale/locale_feature_pod_controller.h",
     "system/locale/locale_notification_controller.cc",
     "system/locale/locale_notification_controller.h",
+    "system/locale/unified_locale_detailed_view_controller.cc",
+    "system/locale/unified_locale_detailed_view_controller.h",
     "system/message_center/arc_notification_manager_delegate_impl.cc",
     "system/message_center/arc_notification_manager_delegate_impl.h",
     "system/message_center/ash_message_center_lock_screen_controller.cc",
@@ -1744,6 +1750,7 @@ test("ash_unittests") {
     "system/flag_warning/flag_warning_tray_unittest.cc",
     "system/ime/ime_feature_pod_controller_unittest.cc",
     "system/ime_menu/ime_menu_tray_unittest.cc",
+    "system/locale/locale_feature_pod_controller_unittest.cc",
     "system/message_center/arc/arc_notification_content_view_unittest.cc",
     "system/message_center/arc/arc_notification_manager_unittest.cc",
     "system/message_center/arc/arc_notification_view_unittest.cc",

ash/ash_strings.grd

@@ -543,6 +543,12 @@ This file contains the strings for ash.
       <message name="IDS_ASH_STATUS_TRAY_NOTIFICATIONS_DO_NOT_DISTURB_SUBLABEL" desc="The sub label text shown under do not disturb button when all notifications are disabled.">
         Do not disturb
       </message>
+      <message name="IDS_ASH_STATUS_TRAY_LOCALE" desc="The label used for locale button in system tray bubble.">
+        Language
+      </message>
+      <message name="IDS_ASH_STATUS_TRAY_LOCALE_TITLE" desc="The title shown in the locale detailed view.">
+        Languages
+      </message>
 
       <!-- Status tray supervised users. -->
       <message name="IDS_ASH_STATUS_TRAY_SUPERVISED_LABEL" desc="Label shown instead of email for supervised users">

ash/public/interfaces/system_tray.mojom

@@ -7,6 +7,15 @@ module ash.mojom;
 import "ash/public/interfaces/update.mojom";
 import "mojo/public/mojom/base/string16.mojom";
 
+// The locale info to show in the locale feature detailed view.
+struct LocaleInfo {
+  // This ISO code of the locale.
+  string iso_code;
+
+  // The display name of the locale.
+  mojo_base.mojom.String16 display_name;
+};
+
 // Allows clients (e.g. Chrome browser) to control the ash system tray menu.
 interface SystemTray {
   // Sets the client interface.
@@ -33,6 +42,10 @@ interface SystemTray {
   // tracing is running.
   SetPerformanceTracingIconVisible(bool visible);
 
+  // Sets the list of supported UI locales. |current_locale_iso_code| refers to
+  // the locale currently used by the UI.
+  SetLocaleList(array<LocaleInfo> locale_list, string current_locale_iso_code);
+
   // Shows an icon in the system tray or a notification on the unified system
   // menu indicating that a software update is available. Once shown, the icon
   // or the notification persists until reboot.
@@ -166,4 +179,8 @@ interface SystemTrayClient {
 
   // Attempts to restart the system for update.
   RequestRestartForUpdate();
+
+  // Sets the UI locale to |locale_iso_code| and exit the session to take
+  // effect.
+  SetLocaleAndExit(string locale_iso_code);
 };

ash/system/locale/locale_detailed_view.cc

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/system/locale/locale_detailed_view.h"
+
+#include "ash/shell.h"
+#include "ash/strings/grit/ash_strings.h"
+#include "ash/system/model/system_tray_model.h"
+#include "ash/system/tray/hover_highlight_view.h"
+#include "base/logging.h"
+#include "ui/views/controls/scroll_view.h"
+
+namespace ash {
+namespace tray {
+
+LocaleDetailedView::LocaleDetailedView(DetailedViewDelegate* delegate)
+    : TrayDetailedView(delegate) {
+  CreateItems();
+}
+
+LocaleDetailedView::~LocaleDetailedView() = default;
+
+void LocaleDetailedView::CreateItems() {
+  CreateTitleRow(IDS_ASH_STATUS_TRAY_LOCALE_TITLE);
+  CreateScrollableList();
+
+  const std::vector<mojom::LocaleInfoPtr>& locales =
+      Shell::Get()->system_tray_model()->locale_list();
+  int id = 0;
+  for (auto& entry : locales) {
+    const bool checked =
+        entry->iso_code ==
+        Shell::Get()->system_tray_model()->current_locale_iso_code();
+    HoverHighlightView* item =
+        AddScrollListCheckableItem(entry->display_name, checked);
+    item->set_id(id);
+    id_to_locale_[id] = entry->iso_code;
+    ++id;
+  }
+  scroll_content()->SizeToPreferredSize();
+  scroller()->Layout();
+  // TODO(wzang): Show locale ISO codes at the beginning of each row, most
+  // likely by reusing the code in |ImeListItemView|.
+}
+
+void LocaleDetailedView::HandleViewClicked(views::View* view) {
+  auto it = id_to_locale_.find(view->id());
+  DCHECK(it != id_to_locale_.end());
+  const std::string locale_iso_code = it->second;
+  if (locale_iso_code !=
+      Shell::Get()->system_tray_model()->current_locale_iso_code()) {
+    Shell::Get()->system_tray_model()->client_ptr()->SetLocaleAndExit(
+        locale_iso_code);
+  }
+}
+
+}  // namespace tray
+}  // namespace ash
\ No newline at end of file

ash/system/locale/locale_detailed_view.h

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_SYSTEM_LOCALE_LOCALE_DETAILED_VIEW_H_
+#define ASH_SYSTEM_LOCALE_LOCALE_DETAILED_VIEW_H_
+
+#include <string>
+
+#include "ash/system/tray/tray_detailed_view.h"
+#include "base/containers/flat_map.h"
+#include "base/macros.h"
+
+namespace ash {
+namespace tray {
+
+// The detailed view to show when the locale feature button is clicked.
+class LocaleDetailedView : public TrayDetailedView {
+ public:
+  explicit LocaleDetailedView(DetailedViewDelegate* delegate);
+  ~LocaleDetailedView() override;
+
+ private:
+  void CreateItems();
+
+  // TrayDetailedView:
+  void HandleViewClicked(views::View* view) override;
+
+  // The map between the id of the view and the locale it corresponds to.
+  base::flat_map<int, std::string> id_to_locale_;
+
+  DISALLOW_COPY_AND_ASSIGN(LocaleDetailedView);
+};
+
+}  // namespace tray
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_LOCALE_LOCALE_DETAILED_VIEW_H_
\ No newline at end of file

ash/system/locale/locale_feature_pod_controller.cc

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/system/locale/locale_feature_pod_controller.h"
+
+#include "ash/resources/vector_icons/vector_icons.h"
+#include "ash/shell.h"
+#include "ash/strings/grit/ash_strings.h"
+#include "ash/system/model/system_tray_model.h"
+#include "ash/system/unified/feature_pod_button.h"
+#include "ash/system/unified/unified_system_tray_controller.h"
+#include "base/strings/utf_string_conversions.h"
+#include "ui/base/l10n/l10n_util.h"
+
+namespace ash {
+
+LocaleFeaturePodController::LocaleFeaturePodController(
+    UnifiedSystemTrayController* tray_controller)
+    : tray_controller_(tray_controller) {}
+
+LocaleFeaturePodController::~LocaleFeaturePodController() = default;
+
+FeaturePodButton* LocaleFeaturePodController::CreateButton() {
+  auto* button = new FeaturePodButton(this);
+  const bool visible =
+      !Shell::Get()->system_tray_model()->locale_list().empty();
+  button->SetVisible(visible);
+  if (visible) {
+    // TODO(wzang): Add a tooltip.
+    // TODO(wzang): |kUnifiedMenuKeyboardIcon| is a placeholder. Change it.
+    button->SetVectorIcon(kUnifiedMenuKeyboardIcon);
+    button->SetLabel(l10n_util::GetStringUTF16(IDS_ASH_STATUS_TRAY_LOCALE));
+    button->ShowDetailedViewArrow();
+    button->DisableLabelButtonFocus();
+    button->SetSubLabel(base::UTF8ToUTF16(
+        Shell::Get()->system_tray_model()->current_locale_iso_code()));
+  }
+  return button;
+}
+
+void LocaleFeaturePodController::OnIconPressed() {
+  tray_controller_->ShowLocaleDetailedView();
+}
+
+SystemTrayItemUmaType LocaleFeaturePodController::GetUmaType() const {
+  return SystemTrayItemUmaType::UMA_LOCALE;
+}
+
+}  // namespace ash

ash/system/locale/locale_feature_pod_controller.h

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_SYSTEM_LOCALE_LOCALE_FEATURE_POD_CONTROLLER_H_
+#define ASH_SYSTEM_LOCALE_LOCALE_FEATURE_POD_CONTROLLER_H_
+
+#include "ash/ash_export.h"
+#include "ash/system/unified/feature_pod_controller_base.h"
+#include "base/macros.h"
+
+namespace ash {
+
+class UnifiedSystemTrayController;
+
+// Controller of locale feature pod button.
+class ASH_EXPORT LocaleFeaturePodController : public FeaturePodControllerBase {
+ public:
+  explicit LocaleFeaturePodController(
+      UnifiedSystemTrayController* tray_controller);
+  ~LocaleFeaturePodController() override;
+
+  // FeaturePodControllerBase:
+  FeaturePodButton* CreateButton() override;
+  void OnIconPressed() override;
+  SystemTrayItemUmaType GetUmaType() const override;
+
+ private:
+  // Unowned.
+  UnifiedSystemTrayController* const tray_controller_;
+
+  DISALLOW_COPY_AND_ASSIGN(LocaleFeaturePodController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_LOCALE_LOCALE_FEATURE_POD_CONTROLLER_H_

ash/system/locale/locale_feature_pod_controller_unittest.cc

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/system/locale/locale_feature_pod_controller.h"
+
+#include <memory>
+#include <vector>
+
+#include "ash/shell.h"
+#include "ash/system/model/system_tray_model.h"
+#include "ash/system/unified/feature_pod_button.h"
+#include "ash/system/unified/unified_system_tray_controller.h"
+#include "ash/system/unified/unified_system_tray_model.h"
+#include "ash/test/ash_test_base.h"
+#include "base/macros.h"
+#include "base/strings/utf_string_conversions.h"
+
+namespace ash {
+namespace {
+
+class LocaleFeaturePodControllerTest : public NoSessionAshTestBase {
+ public:
+  LocaleFeaturePodControllerTest() = default;
+  ~LocaleFeaturePodControllerTest() override = default;
+
+  void SetUp() override {
+    NoSessionAshTestBase::SetUp();
+
+    tray_model_ = std::make_unique<UnifiedSystemTrayModel>();
+    tray_controller_ =
+        std::make_unique<UnifiedSystemTrayController>(tray_model_.get());
+    controller_ =
+        std::make_unique<LocaleFeaturePodController>(tray_controller_.get());
+  }
+
+  void TearDown() override {
+    controller_.reset();
+    tray_controller_.reset();
+    tray_model_.reset();
+    NoSessionAshTestBase::TearDown();
+  }
+
+ protected:
+  std::unique_ptr<LocaleFeaturePodController> controller_;
+
+ private:
+  std::unique_ptr<UnifiedSystemTrayModel> tray_model_;
+  std::unique_ptr<UnifiedSystemTrayController> tray_controller_;
+
+  DISALLOW_COPY_AND_ASSIGN(LocaleFeaturePodControllerTest);
+};
+
+TEST_F(LocaleFeaturePodControllerTest, ButtonVisibility) {
+  constexpr char kDefaultLocaleIsoCode[] = "en-US";
+  // The button is invisible if the locale list is unset.
+  std::unique_ptr<FeaturePodButton> button;
+  button.reset(controller_->CreateButton());
+  EXPECT_FALSE(button->visible());
+
+  // The button is invisible if the locale list is empty.
+  Shell::Get()->system_tray_model()->SetLocaleList(
+      std::vector<mojom::LocaleInfoPtr>(), kDefaultLocaleIsoCode);
+  button.reset(controller_->CreateButton());
+  EXPECT_FALSE(button->visible());
+
+  // The button is visible if the locale list is non-empty.
+  std::vector<mojom::LocaleInfoPtr> locale_list;
+  mojom::LocaleInfoPtr locale = mojom::LocaleInfo::New(
+      kDefaultLocaleIsoCode, base::UTF8ToUTF16("English (United States)"));
+  locale_list.push_back(std::move(locale));
+  Shell::Get()->system_tray_model()->SetLocaleList(std::move(locale_list),
+                                                   kDefaultLocaleIsoCode);
+  button.reset(controller_->CreateButton());
+  EXPECT_TRUE(button->visible());
+}
+
+}  // namespace
+}  // namespace ash
\ No newline at end of file

ash/system/locale/unified_locale_detailed_view_controller.cc

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/system/locale/unified_locale_detailed_view_controller.h"
+
+#include "ash/system/locale/locale_detailed_view.h"
+#include "ash/system/unified/unified_detailed_view_delegate.h"
+#include "base/logging.h"
+
+namespace ash {
+
+UnifiedLocaleDetailedViewController::UnifiedLocaleDetailedViewController(
+    UnifiedSystemTrayController* tray_controller)
+    : detailed_view_delegate_(
+          std::make_unique<UnifiedDetailedViewDelegate>(tray_controller)) {}
+
+UnifiedLocaleDetailedViewController::~UnifiedLocaleDetailedViewController() =
+    default;
+
+views::View* UnifiedLocaleDetailedViewController::CreateView() {
+  DCHECK(!view_);
+  view_ = new tray::LocaleDetailedView(detailed_view_delegate_.get());
+  return view_;
+}
+
+}  // namespace ash

ash/system/locale/unified_locale_detailed_view_controller.h

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_SYSTEM_LOCALE_UNIFIED_LOCALE_DETAILED_VIEW_CONTROLLER_H_
+#define ASH_SYSTEM_LOCALE_UNIFIED_LOCALE_DETAILED_VIEW_CONTROLLER_H_
+
+#include <memory>
+
+#include "ash/system/unified/detailed_view_controller.h"
+#include "base/macros.h"
+
+namespace ash {
+
+namespace tray {
+class LocaleDetailedView;
+}  // namespace tray
+
+class DetailedViewDelegate;
+class UnifiedSystemTrayController;
+
+// Controller of the locale detailed view in UnifiedSystemTray.
+class UnifiedLocaleDetailedViewController : public DetailedViewController {
+ public:
+  explicit UnifiedLocaleDetailedViewController(
+      UnifiedSystemTrayController* tray_controller);
+  ~UnifiedLocaleDetailedViewController() override;
+
+  // DetailedViewControllerBase:
+  views::View* CreateView() override;
+
+ private:
+  const std::unique_ptr<DetailedViewDelegate> detailed_view_delegate_;
+
+  tray::LocaleDetailedView* view_ = nullptr;
+
+  DISALLOW_COPY_AND_ASSIGN(UnifiedLocaleDetailedViewController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_LOCALE_UNIFIED_LOCALE_DETAILED_VIEW_CONTROLLER_H_

ash/system/model/system_tray_model.cc

@@ -67,6 +67,13 @@ void SystemTrayModel::SetPerformanceTracingIconVisible(bool visible) {
   tracing()->SetIsTracing(visible);
 }
 
+void SystemTrayModel::SetLocaleList(
+    std::vector<mojom::LocaleInfoPtr> locale_list,
+    const std::string& current_locale_iso_code) {
+  locale_list_ = std::move(locale_list);
+  current_locale_iso_code_ = current_locale_iso_code;
+}
+
 void SystemTrayModel::ShowUpdateIcon(mojom::UpdateSeverity severity,
                                      bool factory_reset_required,
                                      bool rollback,

ash/system/model/system_tray_model.h

@@ -37,6 +37,8 @@ class SystemTrayModel : public mojom::SystemTray {
   void SetEnterpriseDisplayDomain(const std::string& enterprise_display_domain,
                                   bool active_directory_managed) override;
   void SetPerformanceTracingIconVisible(bool visible) override;
+  void SetLocaleList(std::vector<mojom::LocaleInfoPtr> locale_list,
+                     const std::string& current_locale_iso_code) override;
   void ShowUpdateIcon(mojom::UpdateSeverity severity,
                       bool factory_reset_required,
                       bool rollback,
@@ -59,6 +61,13 @@ class SystemTrayModel : public mojom::SystemTray {
   UpdateModel* update_model() { return update_model_.get(); }
   VirtualKeyboardModel* virtual_keyboard() { return virtual_keyboard_.get(); }
 
+  const std::vector<mojom::LocaleInfoPtr>& locale_list() {
+    return locale_list_;
+  }
+  std::string current_locale_iso_code() const {
+    return current_locale_iso_code_;
+  }
+
   const mojom::SystemTrayClientPtr& client_ptr() { return client_ptr_; }
 
  private:
@@ -69,6 +78,9 @@ class SystemTrayModel : public mojom::SystemTray {
   std::unique_ptr<UpdateModel> update_model_;
   std::unique_ptr<VirtualKeyboardModel> virtual_keyboard_;
 
+  std::vector<mojom::LocaleInfoPtr> locale_list_;
+  std::string current_locale_iso_code_;
+
   // TODO(tetsui): Add following as a sub-model of SystemTrayModel:
   // * BluetoothModel
 

ash/system/tray/system_tray_item_uma_type.h

@@ -42,7 +42,8 @@ enum class SystemTrayItemUmaType {
   UMA_VPN = 25,
   UMA_NIGHT_LIGHT = 26,
   UMA_QUIET_MODE = 27,
-  UMA_COUNT = 28,
+  UMA_LOCALE = 28,
+  UMA_COUNT = 29,
 };
 
 }  // namespace ash

ash/system/unified/unified_system_tray_controller.cc

@@ -20,6 +20,8 @@
 #include "ash/system/cast/unified_cast_detailed_view_controller.h"
 #include "ash/system/ime/ime_feature_pod_controller.h"
 #include "ash/system/ime/unified_ime_detailed_view_controller.h"
+#include "ash/system/locale/locale_feature_pod_controller.h"
+#include "ash/system/locale/unified_locale_detailed_view_controller.h"
 #include "ash/system/model/clock_model.h"
 #include "ash/system/model/system_tray_model.h"
 #include "ash/system/network/network_feature_pod_controller.h"
@@ -265,6 +267,10 @@ void UnifiedSystemTrayController::ShowIMEDetailedView() {
   ShowDetailedView(std::make_unique<UnifiedIMEDetailedViewController>(this));
 }
 
+void UnifiedSystemTrayController::ShowLocaleDetailedView() {
+  ShowDetailedView(std::make_unique<UnifiedLocaleDetailedViewController>(this));
+}
+
 void UnifiedSystemTrayController::ShowAudioDetailedView() {
   ShowDetailedView(std::make_unique<UnifiedAudioDetailedViewController>(this));
 }
@@ -343,6 +349,7 @@ void UnifiedSystemTrayController::InitFeaturePods() {
   AddFeaturePodItem(std::make_unique<AccessibilityFeaturePodController>(this));
   AddFeaturePodItem(std::make_unique<VPNFeaturePodController>(this));
   AddFeaturePodItem(std::make_unique<IMEFeaturePodController>(this));
+  AddFeaturePodItem(std::make_unique<LocaleFeaturePodController>(this));
 
   // If you want to add a new feature pod item, add here.
 }

ash/system/unified/unified_system_tray_controller.h

@@ -85,6 +85,8 @@ class ASH_EXPORT UnifiedSystemTrayController
   void ShowVPNDetailedView();
   // Show the detailed view of IME. Called from the view.
   void ShowIMEDetailedView();
+  // Show the detailed view of locale. Called from the view.
+  void ShowLocaleDetailedView();
   // Show the detailed view of audio. Called from the view.
   void ShowAudioDetailedView();
   // Show the detailed view of notifier settings. Called from the view.

chrome/browser/chromeos/login/demo_mode/demo_session.cc

@@ -10,11 +10,13 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
+#include "base/containers/flat_set.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/optional.h"
 #include "base/stl_util.h"
+#include "base/strings/utf_string_conversions.h"
 #include "base/system/sys_info.h"
 #include "base/task/post_task.h"
 #include "chrome/browser/apps/platform_apps/app_load_service.h"
@@ -25,6 +27,7 @@
 #include "chrome/browser/chromeos/login/demo_mode/demo_setup_controller.h"
 #include "chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h"
 #include "chrome/browser/profiles/profile_manager.h"
+#include "chrome/browser/ui/ash/system_tray_client.h"
 #include "chrome/browser/ui/extensions/app_launch_params.h"
 #include "chrome/browser/ui/extensions/application_launch.h"
 #include "chrome/common/extensions/extension_constants.h"
@@ -40,6 +43,7 @@
 #include "extensions/browser/extension_registry.h"
 #include "extensions/common/constants.h"
 #include "net/base/network_change_notifier.h"
+#include "ui/base/l10n/l10n_util.h"
 
 namespace chromeos {
 
@@ -148,6 +152,36 @@ void RestoreDefaultLocaleForNextSession() {
   }
 }
 
+// Returns the list of locales (and related info) supported by demo mode.
+std::vector<ash::mojom::LocaleInfoPtr> GetSupportedLocales() {
+  const base::flat_set<std::string> kSupportedLocales(
+      {"da", "en-GB", "en-US", "fi", "fr", "fr-CA", "nb", "nl", "sv"});
+
+  const std::vector<std::string>& available_locales =
+      l10n_util::GetAvailableLocales();
+  const std::string current_locale_iso_code =
+      ProfileManager::GetActiveUserProfile()->GetPrefs()->GetString(
+          language::prefs::kApplicationLocale);
+  std::vector<ash::mojom::LocaleInfoPtr> supported_locales;
+  for (const std::string& locale : available_locales) {
+    if (!kSupportedLocales.contains(locale))
+      continue;
+    ash::mojom::LocaleInfoPtr locale_info = ash::mojom::LocaleInfo::New();
+    locale_info->iso_code = locale;
+    locale_info->display_name = l10n_util::GetDisplayNameForLocale(
+        locale, current_locale_iso_code, true /* is_for_ui */);
+    const base::string16 native_display_name =
+        l10n_util::GetDisplayNameForLocale(locale, locale,
+                                           true /* is_for_ui */);
+    if (locale_info->display_name != native_display_name) {
+      locale_info->display_name +=
+          base::UTF8ToUTF16(" - ") + native_display_name;
+    }
+    supported_locales.push_back(std::move(locale_info));
+  }
+  return supported_locales;
+}
+
 }  // namespace
 
 // static
@@ -386,6 +420,14 @@ void DemoSession::OnSessionStateChanged() {
       session_manager::SessionState::ACTIVE) {
     return;
   }
+  // SystemTrayClient may not exist in unit tests.
+  if (SystemTrayClient::Get()) {
+    const std::string current_locale_iso_code =
+        ProfileManager::GetActiveUserProfile()->GetPrefs()->GetString(
+            language::prefs::kApplicationLocale);
+    SystemTrayClient::Get()->SetLocaleList(GetSupportedLocales(),
+                                           current_locale_iso_code);
+  }
   RestoreDefaultLocaleForNextSession();
 
   if (!offline_enrolled_)

chrome/browser/profiles/profile.h

@@ -232,10 +232,12 @@ class Profile : public content::BrowserContext {
     APP_LOCALE_CHANGED_VIA_LOGIN,
     // From login to a public session.
     APP_LOCALE_CHANGED_VIA_PUBLIC_SESSION_LOGIN,
-    // From AllowedLanguages policy
+    // From AllowedLanguages policy.
     APP_LOCALE_CHANGED_VIA_POLICY,
     // From demo session.
     APP_LOCALE_CHANGED_VIA_DEMO_SESSION,
+    // From system tray.
+    APP_LOCALE_CHANGED_VIA_SYSTEM_TRAY,
     // Source unknown.
     APP_LOCALE_CHANGED_VIA_UNKNOWN
   };

chrome/browser/ui/ash/system_tray_client.cc

@@ -20,6 +20,7 @@
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chrome/browser/chromeos/set_time_dialog.h"
 #include "chrome/browser/chromeos/system/system_clock.h"
+#include "chrome/browser/lifetime/application_lifetime.h"
 #include "chrome/browser/lifetime/termination_notification.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/ui/app_list/arc/arc_app_utils.h"
@@ -220,6 +221,12 @@ void SystemTrayClient::SetPerformanceTracingIconVisible(bool visible) {
   system_tray_->SetPerformanceTracingIconVisible(visible);
 }
 
+void SystemTrayClient::SetLocaleList(
+    std::vector<ash::mojom::LocaleInfoPtr> locale_list,
+    const std::string& current_locale_iso_code) {
+  system_tray_->SetLocaleList(std::move(locale_list), current_locale_iso_code);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // ash::mojom::SystemTrayClient:
 
@@ -444,6 +451,12 @@ void SystemTrayClient::RequestRestartForUpdate() {
   browser_shutdown::NotifyAndTerminate(true /* fast_path */, reboot_policy);
 }
 
+void SystemTrayClient::SetLocaleAndExit(const std::string& locale_iso_code) {
+  ProfileManager::GetActiveUserProfile()->ChangeAppLocale(
+      locale_iso_code, Profile::APP_LOCALE_CHANGED_VIA_SYSTEM_TRAY);
+  chrome::AttemptUserExit();
+}
+
 void SystemTrayClient::HandleUpdateAvailable() {
   // Show an update icon for Chrome updates and Flash component updates.
   UpgradeDetector* detector = UpgradeDetector::GetInstance();

chrome/browser/ui/ash/system_tray_client.h

@@ -58,6 +58,8 @@ class SystemTrayClient : public ash::mojom::SystemTrayClient,
   void SetPrimaryTrayEnabled(bool enabled);
   void SetPrimaryTrayVisible(bool visible);
   void SetPerformanceTracingIconVisible(bool visible);
+  void SetLocaleList(std::vector<ash::mojom::LocaleInfoPtr> locale_list,
+                     const std::string& current_locale_iso_code);
 
   // ash::mojom::SystemTrayClient:
   void ShowSettings() override;
@@ -88,6 +90,7 @@ class SystemTrayClient : public ash::mojom::SystemTrayClient,
   void ShowNetworkSettings(const std::string& network_id) override;
   void ShowMultiDeviceSetup() override;
   void RequestRestartForUpdate() override;
+  void SetLocaleAndExit(const std::string& locale_iso_code) override;
 
  private:
   // Helper function shared by ShowNetworkSettings() and ShowNetworkConfigure().

tools/metrics/histograms/enums.xml

@@ -49105,6 +49105,7 @@ would be helpful to identify which type is being sent.
   <int value="25" label="VPN"/>
   <int value="26" label="Night light"/>
   <int value="27" label="Do not disturb"/>
+  <int value="28" label="Language"/>
 </enum>
 
 <enum name="SystemNotificationType">