Beginnings of synchronizing notifications in the notification database.

chrome/browser/notifications/platform_notification_service_impl.h

Index: chrome/browser/notifications/platform_notification_service_impl.h
diff --git a/chrome/browser/notifications/platform_notification_service_impl.h b/chrome/browser/notifications/platform_notification_service_impl.h
index bfbad2d4a189280f328afe075e3c222694943021..777da49cb6e298c67dc22f0d6b0933ee32be757e 100644
--- a/chrome/browser/notifications/platform_notification_service_impl.h
+++ b/chrome/browser/notifications/platform_notification_service_impl.h
@@ -78,6 +78,9 @@ class PlatformNotificationServiceImpl
   void ClosePersistentNotification(
       content::BrowserContext* browser_context,
       int64_t persistent_notification_id) override;
+  bool GetDisplayedPersistentNotifications(
+      content::BrowserContext* browser_context,
+      std::set<std::string>* displayed_notifications) override;
 
  private:
   friend struct DefaultSingletonTraits<PlatformNotificationServiceImpl>;