Migrate upgrade notifications to observer

chrome/browser/ui/ash/system_tray_client.h

Index: chrome/browser/ui/ash/system_tray_client.h
diff --git a/chrome/browser/ui/ash/system_tray_client.h b/chrome/browser/ui/ash/system_tray_client.h
index 12fa7915e65fff5b834a2a9087ecec2354cfd283..1237ff224d98692d83379e4de7a80785ce70458d 100644
--- a/chrome/browser/ui/ash/system_tray_client.h
+++ b/chrome/browser/ui/ash/system_tray_client.h
@@ -10,8 +10,6 @@
 #include "chrome/browser/chromeos/system/system_clock_observer.h"
 #include "chrome/browser/upgrade_observer.h"
 #include "components/policy/core/common/cloud/cloud_policy_store.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace ash {
@@ -29,7 +27,6 @@ class WidgetDelegate;
 class SystemTrayClient : public ash::mojom::SystemTrayClient,
                          public chromeos::system::SystemClockObserver,
                          public policy::CloudPolicyStore::Observer,
-                         public content::NotificationObserver,
                          public UpgradeObserver {
  public:
   SystemTrayClient();
@@ -101,8 +98,9 @@ class SystemTrayClient : public ash::mojom::SystemTrayClient,
   // chromeos::system::SystemClockObserver:
   void OnSystemClockChanged(chromeos::system::SystemClock* clock) override;
 
-  // UpgradeObserver:
+  // UpgradeObserver implementation.
   void OnUpdateOverCellularAvailable() override;
+  void OnUpgradeRecommended() override;
 
   // policy::CloudPolicyStore::Observer
   void OnStoreLoaded(policy::CloudPolicyStore* store) override;
@@ -110,11 +108,6 @@ class SystemTrayClient : public ash::mojom::SystemTrayClient,
 
   void UpdateEnterpriseDomain();
 
-  // content::NotificationObserver:
-  void Observe(int type,
-               const content::NotificationSource& source,
-               const content::NotificationDetails& details) override;
-
   // System tray mojo service in ash.
   ash::mojom::SystemTrayPtr system_tray_;
 
@@ -129,8 +122,6 @@ class SystemTrayClient : public ash::mojom::SystemTrayClient,
   std::string last_enterprise_domain_;
   bool last_active_directory_managed_ = false;
 
-  content::NotificationRegistrar registrar_;
-
   DISALLOW_COPY_AND_ASSIGN(SystemTrayClient);
 };