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

chrome/browser/ui/webui/signin/login_ui_service.h

Index: chrome/browser/ui/webui/signin/login_ui_service.h
===================================================================
--- chrome/browser/ui/webui/signin/login_ui_service.h	(revision 145382)
+++ chrome/browser/ui/webui/signin/login_ui_service.h	(working copy)
@@ -7,6 +7,7 @@
 #pragma once
 
 #include "base/basictypes.h"
+#include "base/observer_list.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 
 class Browser;
@@ -29,6 +30,14 @@
     virtual ~LoginUI() {}
   };
 
+  class Observer {
+   public:
+    // Called when a new login UI is shown.
+    virtual void OnLoginUIShown(LoginUI* ui) = 0;
+    // Called when a login UI is closed.
+    virtual void OnLoginUIClosed(LoginUI* ui) = 0;
+  };
+
   LoginUIService();
   virtual ~LoginUIService();
 
@@ -37,12 +46,17 @@
     return ui_;
   }
 
+  void AddObserver(Observer* o);

[jam, 2012/07/10 16:13:07]

nit: Observer* observer

[Munjal (Google), 2012/07/10 16:46:15]

Done.

+  void RemoveObserver(Observer* o);
+
   // Sets the currently active login UI. It is illegal to call this if there is
   // already login UI visible.
+  // Fires chrome::NOTIFICATION_LOGIN_UI_CHANGED.

[jam, 2012/07/10 16:13:07]

nit: remove this comment and below

[Munjal (Google), 2012/07/10 16:46:15]

Done.

   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.
+  // Fires chrome::NOTIFICATION_LOGIN_UI_CHANGED.
   void LoginUIClosed(LoginUI* ui);
 
   // Brings the login UI to the foreground, or if there is no login UI,
@@ -54,6 +68,8 @@
   // Weak pointer to the currently active login UI, or null if none.
   LoginUI* ui_;
 
+  ObserverList<Observer> observer_list_;
+
   DISALLOW_COPY_AND_ASSIGN(LoginUIService);
 };