chromeos: Replace user image notifications with observer

chrome/browser/ui/ash/system_tray_delegate_chromeos.h

Index: chrome/browser/ui/ash/system_tray_delegate_chromeos.h
diff --git a/chrome/browser/ui/ash/system_tray_delegate_chromeos.h b/chrome/browser/ui/ash/system_tray_delegate_chromeos.h
index 012ac31347e959ff3ad61a442fe173685aa44ca8..668fd0f838668c950fd959fe8048b856c2fd04b2 100644
--- a/chrome/browser/ui/ash/system_tray_delegate_chromeos.h
+++ b/chrome/browser/ui/ash/system_tray_delegate_chromeos.h
@@ -62,6 +62,7 @@ class SystemTrayDelegateChromeOS
       public ash::SessionStateObserver,
       public chrome::BrowserListObserver,
       public extensions::AppWindowRegistry::Observer,
+      public user_manager::UserManager::Observer,
       public user_manager::UserManager::UserSessionStateObserver,
       public SupervisedUserServiceObserver,
       public input_method::InputMethodManager::ImeMenuObserver {
@@ -116,6 +117,9 @@ class SystemTrayDelegateChromeOS
   std::unique_ptr<ash::SystemTrayItem> CreateRotationLockTrayItem(
       ash::SystemTray* tray) override;
 
+  // Overridden from user_manager::UserManager::Observer:
+  void OnUserImageChanged(const user_manager::User& user) override;
+
   // Overridden from user_manager::UserManager::UserSessionStateObserver:
   void UserAddedToSession(const user_manager::User* active_user) override;
   void ActiveUserChanged(const user_manager::User* active_user) override;