ash: Merge LoginStatus update code path

ash/common/session/session_state_observer.h

Index: ash/common/session/session_state_observer.h
diff --git a/ash/common/session/session_state_observer.h b/ash/common/session/session_state_observer.h
index 83aefd7e74bc175d75949c962079119fcf8bb222..5f2d344686f89b51070d4c700f116daf68778007 100644
--- a/ash/common/session/session_state_observer.h
+++ b/ash/common/session/session_state_observer.h
@@ -13,6 +13,8 @@ class AccountId;
 
 namespace ash {
 
+enum class LoginStatus;
+
 class ASH_EXPORT SessionStateObserver {
  public:
   // Called when active user has changed.
@@ -24,9 +26,12 @@ class ASH_EXPORT SessionStateObserver {
   // Called when a user session is updated, such as avatar change.
   virtual void UserSessionUpdated(const AccountId& account_id) {}
 
-  // Called when session state is changed.
+  // Called when the session state is changed.
   virtual void SessionStateChanged(session_manager::SessionState state) {}
 
+  // Called when the login status is changed. |login_status| is the new status.
+  virtual void LoginStatusChanged(LoginStatus login_status) {}
+
  protected:
   virtual ~SessionStateObserver() {}
 };