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

chrome/browser/chromeos/upgrade_detector_chromeos.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 CHROME_BROWSER_CHROMEOS_UPGRADE_DETECTOR_CHROMEOS_H_
 #define CHROME_BROWSER_CHROMEOS_UPGRADE_DETECTOR_CHROMEOS_H_
 
 #include "base/compiler_specific.h"
+#include "base/memory/weak_ptr.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/upgrade_detector.h"
 #include "chromeos/dbus/update_engine_client.h"
 
 template <typename T> struct DefaultSingletonTraits;
 
 class UpgradeDetectorChromeos : public UpgradeDetector,
                                 public chromeos::UpdateEngineClient::Observer {
  public:
   virtual ~UpgradeDetectorChromeos();
 
   static UpgradeDetectorChromeos* GetInstance();
 
   // Initializes the object. Starts observing changes from the update
   // engine.
   void Init();
 
   // Shuts down the object. Stops observing observe changes from the
   // update engine.
   void Shutdown();
 
  private:
   friend struct DefaultSingletonTraits<UpgradeDetectorChromeos>;
+  class ChannelsRequester;
 
   UpgradeDetectorChromeos();
 
   // chromeos::UpdateEngineClient::Observer implementation.
   virtual void UpdateStatusChanged(
       const chromeos::UpdateEngineClient::Status& status) override;
 
   // The function that sends out a notification (after a certain time has
   // elapsed) that lets the rest of the UI know we should start notifying the
   // user that a new version is available.
   void NotifyOnUpgrade();
 
+  void OnChannelsReceived(const std::string& current_channel,
+                          const std::string& target_channel);
+
   // After we detect an upgrade we start a recurring timer to see if enough time
   // has passed and we should start notifying the user.
   base::RepeatingTimer<UpgradeDetectorChromeos> upgrade_notification_timer_;
   bool initialized_;
   base::Time upgrade_detected_time_;
 
+  scoped_ptr<ChannelsRequester> channels_requester_;
+
+  base::WeakPtrFactory<UpgradeDetectorChromeos> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(UpgradeDetectorChromeos);
 };
 
 #endif  // CHROME_BROWSER_CHROMEOS_UPGRADE_DETECTOR_CHROMEOS_H_