Access to Chrome via the System Tray should go through the User Manager.

chrome/browser/ui/views/profiles/user_manager_view.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_VIEWS_PROFILES_USER_MANAGER_VIEW_H_
 #define CHROME_BROWSER_UI_VIEWS_PROFILES_USER_MANAGER_VIEW_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_window.h"
 #include "ui/views/window/dialog_delegate.h"
 
 class AutoKeepAlive;
 
 namespace views {
 class WebView;
 }
 
 // Dialog widget that contains the Desktop User Manager webui.
 class UserManagerView : public views::DialogDelegateView {
  public:
-  // Shows the User Manager or re-activates an existing one, focusing the
-  // profile given by |profile_path_to_focus|. Based on the value of
-  // |tutorial_mode|, a tutorial could be shown, in which case
-  // |profile_path_to_focus| is ignored.
-  static void Show(const base::FilePath& profile_path_to_focus,
-                   profiles::UserManagerTutorialMode tutorial_mode);
-
-  // Hide the User Manager.
-  static void Hide();
-
-  // Returns whether or not the User Manager is showing.
-  static bool IsShowing();
-
- private:
-  friend struct base::DefaultDeleter<UserManagerView>;
-
+  // Do not call directly. To display the User Manager, use UserManager::Show().
   UserManagerView();
-  virtual ~UserManagerView();
 
   // Creates a new UserManagerView instance for the |guest_profile| and
   // shows the |url|.
   static void OnGuestProfileCreated(scoped_ptr<UserManagerView> instance,
                                     const base::FilePath& profile_path_to_focus,
                                     Profile* guest_profile,
                                     const std::string& url);
 
+ private:
+  virtual ~UserManagerView();
+
+  friend struct base::DefaultDeleter<UserManagerView>;
+
   // Creates dialog and initializes UI.
   void Init(const base::FilePath& profile_path_to_focus,
             Profile* guest_profile,
             const GURL& url);
 
   // views::View:
   virtual bool AcceleratorPressed(const ui::Accelerator& accelerator) OVERRIDE;
   virtual gfx::Size GetPreferredSize() const OVERRIDE;
 
   // views::DialogDelegateView:
   virtual bool CanResize() const OVERRIDE;
   virtual bool CanMaximize() const OVERRIDE;
   virtual base::string16 GetWindowTitle() const OVERRIDE;
   virtual int GetDialogButtons() const OVERRIDE;
   virtual void WindowClosing() OVERRIDE;
   virtual bool UseNewStyleForThisDialog() const OVERRIDE;
 
   views::WebView* web_view_;
 
   scoped_ptr<AutoKeepAlive> keep_alive_;
-  // 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 UserManagerView* instance_;
 
   DISALLOW_COPY_AND_ASSIGN(UserManagerView);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_PROFILES_USER_MANAGER_VIEW_H_