Adding "UserAddedToSession" notifier to the SessionStateObserver

chrome/browser/chromeos/login/user_manager.h

Index: chrome/browser/chromeos/login/user_manager.h
diff --git a/chrome/browser/chromeos/login/user_manager.h b/chrome/browser/chromeos/login/user_manager.h
index a44f0b0efc51544301ea85be60d71ba6014d5952..61b19ce400d6885036fd343379a6276b743e620a 100644
--- a/chrome/browser/chromeos/login/user_manager.h
+++ b/chrome/browser/chromeos/login/user_manager.h
@@ -40,6 +40,9 @@ class UserManager {
     // Called when active user has changed.
     virtual void ActiveUserChanged(const User* active_user);
 
+    // Called when another user got added to the existing session.
+    virtual void UserAddedToSession(const User* added_user);
+
     // Called right before notifying on user change so that those who rely
     // on user_id hash would be accessing up-to-date value.
     virtual void ActiveUserHashChanged(const std::string& hash);