Modal window in user session not blocks user adding screen.

ash/session_state_delegate.h

Index: ash/session_state_delegate.h
diff --git a/ash/session_state_delegate.h b/ash/session_state_delegate.h
index d3ecac8a5604f2be0fea691825910a679aa23ec7..0f2c569c5125bbea82c49e6056f9e0cb3c76f0a6 100644
--- a/ash/session_state_delegate.h
+++ b/ash/session_state_delegate.h
@@ -56,6 +56,11 @@ class ASH_EXPORT SessionStateDelegate {
   // Unlocks the screen.
   virtual void UnlockScreen() = 0;
 
+  // Returns |true| if user session blocked by some overlying UI. It can be
+  // login screen, lock screen or screen for adding users into multi-profile
+  // session.
+  virtual bool IsUserSessionBlocked() const = 0;
+
   // Gets the displayed name for the user with the given |index|.
   // Note that |index| can at maximum be |NumberOfLoggedInUsers() - 1|.
   virtual const base::string16 GetUserDisplayName(