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

ash/system/tray/system_tray_delegate.h

Index: ash/system/tray/system_tray_delegate.h
diff --git a/ash/system/tray/system_tray_delegate.h b/ash/system/tray/system_tray_delegate.h
index 4df2f70452f6576632d8df5c2b866bf3a2cf7272..a1f298a3975a86f089d13e1882f0665c0d6dd3cd 100644
--- a/ash/system/tray/system_tray_delegate.h
+++ b/ash/system/tray/system_tray_delegate.h
@@ -75,6 +75,21 @@ struct ASH_EXPORT IMEInfo {
   base::string16 short_name;
 };
 
+struct ASH_EXPORT UpdateInfo {
+  enum UpdateSeverity {
+    UPDATE_NORMAL,
+    UPDATE_LOW_GREEN,
+    UPDATE_HIGH_ORANGE,
+    UPDATE_SEVERE_RED,
+  };
+
+  UpdateInfo();
+  ~UpdateInfo();
+
+  UpdateSeverity severity;
+  bool is_factory_reset_required;
+};
+
 typedef std::vector<IMEInfo> IMEInfoList;
 
 class VolumeControlDelegate;
@@ -121,8 +136,9 @@ class ASH_EXPORT SystemTrayDelegate {
   // Returns true if the current user is supervised.
   virtual bool IsUserSupervised() const = 0;
 
-  // Returns whether a system upgrade is available.
-  virtual bool SystemShouldUpgrade() const = 0;
+  // Returns whether a system upgrade is available. Fills |info| structure if
+  // it's not NULL.
+  virtual bool SystemShouldUpgrade(UpdateInfo* info) const = 0;

[stevenjb, 2014/10/01 22:26:44]

Looking at the chrome implementation, it looks like this should actually be
'GetSystemUpdateInfoAndNotify()' with a better comment. 

We should also make 'update_required' part of UpdateInfo instead of returning a
bool.

[ygorshenin1, 2014/10/02 14:21:35]

I renamed the method to GetSystemUpdateInfo(), but why it should have the suffix
"AndNotify"? It's a job of SystemTrayNotifier to notify observers about events.

On 2014/10/01 22:26:44, stevenjb wrote:

[stevenjb, 2014/10/02 15:33:55]

Sorry, that was some intermediate confusion on my part. I was looking at the
chromeos implementation and got confused by the
UpgradeDetector::notify_upgrade() method (which should really be named something
like should_notify, but probably not here).
Anyway, please ignore that, sorry for the confusion.

 
   // Returns the desired hour clock type.
   virtual base::HourClockType GetHourClockType() const = 0;