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

chrome/browser/chromeos/upgrade_detector_chromeos.h

Index: chrome/browser/chromeos/upgrade_detector_chromeos.h
diff --git a/chrome/browser/chromeos/upgrade_detector_chromeos.h b/chrome/browser/chromeos/upgrade_detector_chromeos.h
index cbd299793744941d695b11c5215c1f8256d52db1..b13ff9a45158028b0a1dd769c423d51ccb4ae0a4 100644
--- a/chrome/browser/chromeos/upgrade_detector_chromeos.h
+++ b/chrome/browser/chromeos/upgrade_detector_chromeos.h
@@ -6,6 +6,7 @@
 #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"
@@ -29,6 +30,7 @@ class UpgradeDetectorChromeos : public UpgradeDetector,
 
  private:
   friend struct DefaultSingletonTraits<UpgradeDetectorChromeos>;
+  class ChannelsRequester;
 
   UpgradeDetectorChromeos();
 
@@ -41,12 +43,19 @@ class UpgradeDetectorChromeos : public UpgradeDetector,
   // 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);
 };