Added Aura notification that relaunch and powerwash is required in case of downgrade.

ash/system/tray/default_system_tray_delegate.h

 // Copyright 2013 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_DEFAULT_SYSTEM_TRAY_DELEGATE_H_
 #define ASH_SYSTEM_TRAY_DEFAULT_SYSTEM_TRAY_DELEGATE_H_
 
 #include "ash/ash_export.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace ash {
 
 class ASH_EXPORT DefaultSystemTrayDelegate : public SystemTrayDelegate {
  public:
   DefaultSystemTrayDelegate();
   virtual ~DefaultSystemTrayDelegate();
 
   // Overridden from SystemTrayDelegate:
   virtual void Initialize() override;
   virtual void Shutdown() override;
   virtual bool GetTrayVisibilityOnStartup() override;
   virtual user::LoginStatus GetUserLoginStatus() const override;
   virtual void ChangeProfilePicture() override;
   virtual const std::string GetEnterpriseDomain() const override;
   virtual const base::string16 GetEnterpriseMessage() const override;
   virtual const std::string GetSupervisedUserManager() const override;
-  virtual const base::string16 GetSupervisedUserManagerName() const
-      override;
+  virtual const base::string16 GetSupervisedUserManagerName() const override;
   virtual const base::string16 GetSupervisedUserMessage() const override;
   virtual bool IsUserSupervised() const override;
-  virtual bool SystemShouldUpgrade() const override;
+  virtual void GetSystemUpdateInfo(UpdateInfo* info) const override;
   virtual base::HourClockType GetHourClockType() const override;
   virtual void ShowSettings() override;
   virtual bool ShouldShowSettings() override;
   virtual void ShowDateSettings() override;
   virtual void ShowSetTimeDialog() override;
   virtual void ShowNetworkSettings(const std::string& service_path) override;
   virtual void ShowBluetoothSettings() override;
   virtual void ShowDisplaySettings() override;
   virtual void ShowChromeSlow() override;
   virtual bool ShouldShowDisplayNotification() override;
@@ skipping 49 matching lines @@
  private:
   bool bluetooth_enabled_;
   scoped_ptr<VolumeControlDelegate> volume_control_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultSystemTrayDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_DEFAULT_SYSTEM_TRAY_DELEGATE_H_