Implements a display scale tray setting behind a chrome switch

ash/system/tray/system_tray.h

 // Copyright (c) 2012 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_TRAY_SYSTEM_TRAY_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 12 matching lines @@
 class ScreenTrayItem;
 class SystemBubbleWrapper;
 class SystemTrayDelegate;
 class SystemTrayItem;
 class TrayAccessibility;
 class TrayAudio;
 class TrayCast;
 class TrayEnterprise;
 class TrayNetwork;
 class TrayNightLight;
+class TrayScale;
 class TraySupervisedUser;
 class TraySystemInfo;
 class TrayTiles;
 class TrayUpdate;
 class WebNotificationTray;
 
 // There are different methods for creating bubble views.
 enum BubbleCreationType {
   BUBBLE_CREATE_NEW,    // Closes any existing bubble and creates a new one.
   BUBBLE_USE_EXISTING,  // Uses any existing bubble, or creates a new one.
@@ skipping 184 matching lines @@
   // Note that the value is only valid when |system_bubble_| is true.
   bool full_system_tray_menu_ = false;
 
   // These objects are not owned by this class.
   TrayAccessibility* tray_accessibility_ = nullptr;
   TrayAudio* tray_audio_ = nullptr;
   TrayCast* tray_cast_ = nullptr;
   TrayEnterprise* tray_enterprise_ = nullptr;
   TrayNetwork* tray_network_ = nullptr;
   TrayTiles* tray_tiles_ = nullptr;
+  TrayScale* tray_scale_ = nullptr;
   TraySupervisedUser* tray_supervised_user_ = nullptr;
   TraySystemInfo* tray_system_info_ = nullptr;
   TrayUpdate* tray_update_ = nullptr;
   TrayNightLight* tray_night_light_ = nullptr;
 
   // A reference to the Screen share and capture item.
   ScreenTrayItem* screen_capture_tray_item_ = nullptr;  // not owned
   ScreenTrayItem* screen_share_tray_item_ = nullptr;    // not owned
 
   std::unique_ptr<KeyEventWatcher> key_event_watcher_;
 
   std::unique_ptr<ActivationObserver> activation_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_