Adding user into session doesn't generate login-prompt-visible.

chrome/browser/chromeos/login/webui_login_view.h

 // Copyright (c) 2012 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 CHROME_BROWSER_CHROMEOS_LOGIN_WEBUI_LOGIN_VIEW_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_WEBUI_LOGIN_VIEW_H_
 
 #include <map>
 #include <string>
 
@@ skipping 83 matching lines @@
   void OnPostponedShow();
 
   // Toggles status area visibility.
   void SetStatusAreaVisible(bool visible);
 
   // Sets whether UI should be enabled.
   void SetUIEnabled(bool enabled);
 
   void set_is_hidden(bool hidden) { is_hidden_ = hidden; }
 
- protected:
-  // Let non-login derived classes suppress emission of this signal.
+  // Let suppress emission of this signal.
   void set_should_emit_login_prompt_visible(bool emit) {
     should_emit_login_prompt_visible_ = emit;
   }
 
+ protected:
   // Overridden from views::View:
   virtual void Layout() OVERRIDE;
   virtual void OnLocaleChanged() OVERRIDE;
   virtual void ChildPreferredSizeChanged(View* child) OVERRIDE;
   virtual void AboutToRequestFocusFromTabTraversal(bool reverse) OVERRIDE;
 
   // Overridden from content::NotificationObserver.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
@@ skipping 59 matching lines @@
   scoped_ptr<ScopedGaiaAuthExtension> auth_extension_;
 
   ObserverList<web_modal::WebContentsModalDialogHostObserver> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(WebUILoginView);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_WEBUI_LOGIN_VIEW_H_