Providing more information on why certain users can't be added to multi-profile

ash/session/session_state_delegate.h

Index: ash/session/session_state_delegate.h
diff --git a/ash/session/session_state_delegate.h b/ash/session/session_state_delegate.h
index 89c1ff8d4f951d2bd76630ebddfaf86f17107b8c..6f846473751ca5b2a6da82fe1f5fcf6e975d06f4 100644
--- a/ash/session/session_state_delegate.h
+++ b/ash/session/session_state_delegate.h
@@ -134,6 +134,9 @@ class ASH_EXPORT SessionStateDelegate {
   // ordering as GetLoggedInUsers.
   virtual void CycleActiveUser(CycleUser cycle_user) = 0;
 
+  // Returns true if primary user policy does not forbid multiple signin.
+  virtual bool IsMultiProfileAllowedByPrimaryUserPolicy() const = 0;
+
   // Adds or removes sessions state observer.
   virtual void AddSessionStateObserver(SessionStateObserver* observer) = 0;
   virtual void RemoveSessionStateObserver(SessionStateObserver* observer) = 0;