The User Manager should be backed by a special profile, not the guest one.

chrome/browser/ui/cocoa/profiles/user_manager_mac.h

 // Copyright 2014 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_UI_COCOA_PROFILES_USER_MANAGER_MAC_H_
 #define CHROME_BROWSER_UI_COCOA_PROFILES_USER_MANAGER_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/scoped_nsobject.h"
@@ skipping 26 matching lines @@
   static bool IsShowing();
 
   // Called by the cocoa window controller when its window closes and the
   // controller destroyed itself. Deletes the instance.
   void WindowWasClosed();
 
  private:
   explicit UserManagerMac(Profile* profile);
   virtual ~UserManagerMac();
 
-  // Creates a new UserManagerMac instance for the |guest_profile| and
-  // shows the |url|.
-  static void OnGuestProfileCreated(Profile* guest_profile,
-                                    const std::string& url);
+  // Creates a new UserManagerMac instance for |profile| and shows the |url|.
+  static void OnUserManagerProfileCreated(Profile* profile,
+                                          const std::string& url);
 
   // An open User Manager window. There can only be one open at a time. This
   // is reset to NULL when the window is closed.
   static UserManagerMac* instance_;  // Weak.
 
   // Controller of the window.
   base::scoped_nsobject<UserManagerWindowController> window_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(UserManagerMac);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_PROFILES_USER_MANAGER_MAC_H_