Modal window in user session not blocks user adding screen.

ash/session_state_delegate.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_SESSION_STATE_DELEGATE_H_
 #define ASH_SESSION_STATE_DELEGATE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 38 matching lines @@
 
   // Returns true if the screen is currently locked.
   virtual bool IsScreenLocked() const = 0;
 
   // Locks the screen. The locking happens asynchronously.
   virtual void LockScreen() = 0;
 
   // 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(
       MultiProfileIndex index) const = 0;
 
   // Gets the email address for the user with the given |index|.
   // Note that |index| can at maximum be |NumberOfLoggedInUsers() - 1|.
   virtual const std::string GetUserEmail(MultiProfileIndex index) const = 0;
 
   // Gets the avatar image for the user with the given |index|.
   // Note that |index| can at maximum be |NumberOfLoggedInUsers() - 1|.
   virtual const gfx::ImageSkia& GetUserImage(MultiProfileIndex index) const = 0;
 
   // Returns a list of all logged in users.
   virtual void GetLoggedInUsers(UserIdList* users) = 0;
 
   // Switches to another active user (if that user has already signed in).
   virtual void SwitchActiveUser(const std::string& user_id) = 0;
 
   // Adds or removes sessions state observer.
   virtual void AddSessionStateObserver(SessionStateObserver* observer) = 0;
   virtual void RemoveSessionStateObserver(SessionStateObserver* observer) = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_SESSION_STATE_DELEGATE_H_