Add a method to LoginUIService to open the sign in UI in a popup.

chrome/browser/ui/webui/signin/login_ui_service.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_UI_WEBUI_SIGNIN_LOGIN_UI_SERVICE_H_
 #define CHROME_BROWSER_UI_WEBUI_SIGNIN_LOGIN_UI_SERVICE_H_
 #pragma once
 
 #include "base/basictypes.h"
+#include "base/observer_list.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 
 class Browser;
 
 // The LoginUIService helps track per-profile information for the login UI -
 // for example, whether there is login UI currently on-screen.
 class LoginUIService : public ProfileKeyedService {
  public:
   // Various UI components implement this API to allow LoginUIService to
   // manipulate their associated login UI.
   class LoginUI {
    public:
     // Invoked when the login UI should be brought to the foreground.
     virtual void FocusUI() = 0;
 
     // Invoked when the login UI should be closed. This can be invoked if the
     // user takes an action that should display new login UI.
     virtual void CloseUI() = 0;
    protected:
     virtual ~LoginUI() {}
   };
 
+  // Interface for obervers of LoginUIService.
+  class Observer {
+   public:
+    // Called when a new login UI is shown.
+    // |ui| The login UI that was just shown. Will never be null.
+    virtual void OnLoginUIShown(LoginUI* ui) = 0;
+
+    // Called when a login UI is closed.
+    // |ui| The login UI that was just closed; will never be null.
+    virtual void OnLoginUIClosed(LoginUI* ui) = 0;
+
+   protected:
+    virtual ~Observer() {}
+  };
+
   LoginUIService();
   virtual ~LoginUIService();
 
   // Gets the currently active login UI, or null if no login UI is active.
   LoginUI* current_login_ui() const {
     return ui_;
   }
 
+  // |observer| The observer to add or remove; cannot be NULL.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
   // Sets the currently active login UI. It is illegal to call this if there is
   // already login UI visible.
   void SetLoginUI(LoginUI* ui);
 
   // Called when login UI is closed. If the passed UI is the current login UI,
   // sets current_login_ui() to null.
   void LoginUIClosed(LoginUI* ui);
 
   // Brings the login UI to the foreground, or if there is no login UI,
   // navigates to the login UI page in the given browser.
   // Virtual for mocking purposes.
   virtual void ShowLoginUI(Browser* browser);
 
  private:
   // Weak pointer to the currently active login UI, or null if none.
   LoginUI* ui_;
 
+  // List of observers.
+  ObserverList<Observer> observer_list_;
+
   DISALLOW_COPY_AND_ASSIGN(LoginUIService);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SIGNIN_LOGIN_UI_SERVICE_H_