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

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

 // 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.
 
 #include "chrome/browser/ui/webui/signin/login_ui_service.h"
 
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/chrome_pages.h"
 #include "chrome/common/url_constants.h"
 
 LoginUIService::LoginUIService() : ui_(NULL) {
 }
 
 LoginUIService::~LoginUIService() {}
 
+void LoginUIService::AddObserver(Observer* observer) {
+  observer_list_.AddObserver(observer);
+}
+
+void LoginUIService::RemoveObserver(Observer* observer) {
+  observer_list_.RemoveObserver(observer);
+}
+
 void LoginUIService::SetLoginUI(LoginUI* ui) {
   DCHECK(!current_login_ui() || current_login_ui() == ui);
   ui_ = ui;
+  FOR_EACH_OBSERVER(Observer, observer_list_, OnLoginUIShown(ui_));
 }
 
 void LoginUIService::LoginUIClosed(LoginUI* ui) {
-  if (current_login_ui() == ui)
-    ui_ = NULL;
+  if (current_login_ui() != ui)
+    return;
+
+  FOR_EACH_OBSERVER(Observer, observer_list_, OnLoginUIClosed(ui_));
+  ui_ = NULL;

[Andrew T Wilson (Slow), 2012/07/10 17:37:43]

I would suggest clearing ui_ here before notifying observers. That way, if an
observer wants to call SetLoginUI for some reason, they can do so.

[Munjal (Google), 2012/07/10 18:02:58]

Done.

 }
 
 void LoginUIService::ShowLoginUI(Browser* browser) {
   if (ui_) {
     // We already have active login UI - make it visible.
     ui_->FocusUI();
     return;
   }
 
   // Need to navigate to the settings page and display the UI.
   chrome::ShowSettingsSubPage(browser, chrome::kSyncSetupSubPage);
 }