Introduce ability to register callback with GoogleURLTracker

chrome/browser/search_engines/template_url_service.h

Index: chrome/browser/search_engines/template_url_service.h
diff --git a/chrome/browser/search_engines/template_url_service.h b/chrome/browser/search_engines/template_url_service.h
index 8d5f5537a4e1022d3e16e712c825e9609f3d809e..18513c38a4007a5b8febda3687907e8f1cc84ed4 100644
--- a/chrome/browser/search_engines/template_url_service.h
+++ b/chrome/browser/search_engines/template_url_service.h
@@ -328,6 +328,9 @@ class TemplateURLService : public WebDataServiceConsumer,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Callback that is called when the Google URL is updated.
+  void OnGoogleURLUpdated(GURL old_url, GURL new_url);
+
   // KeyedService implementation.
   virtual void Shutdown() OVERRIDE;
 
@@ -772,6 +775,9 @@ class TemplateURLService : public WebDataServiceConsumer,
   // Helper class to manage the default search engine.
   DefaultSearchManager default_search_manager_;
 
+  scoped_ptr<base::CallbackList<void(GURL, GURL)>::Subscription>
+      google_url_updated_subscription_;
+
   // Used to disable the prepopulated search engines in tests.
   static bool g_fallback_search_engines_disabled;