Retrive displayed notifications asynchronously

content/public/browser/platform_notification_service.h

Index: content/public/browser/platform_notification_service.h
diff --git a/content/public/browser/platform_notification_service.h b/content/public/browser/platform_notification_service.h
index c1ad9ecd12d03f138b9723274bd68626e4583cad..edb74805bf56848abd97e1de09a9979c7bf40fb6 100644
--- a/content/public/browser/platform_notification_service.h
+++ b/content/public/browser/platform_notification_service.h
@@ -84,6 +84,11 @@ class CONTENT_EXPORT PlatformNotificationService {
   virtual bool GetDisplayedNotifications(
       BrowserContext* browser_context,
       std::set<std::string>* displayed_notifications) = 0;
+
+  virtual void GetDisplayedNotificationsAsync(
+      BrowserContext* browser_context,
+      const base::Callback<void(std::unique_ptr<std::set<std::string>>,
+                                bool /* success */)>&) = 0;
 };
 
 }  // namespace content