Retrive displayed notifications asynchronously

chrome/browser/notifications/notification_display_service.h

Index: chrome/browser/notifications/notification_display_service.h
diff --git a/chrome/browser/notifications/notification_display_service.h b/chrome/browser/notifications/notification_display_service.h
index 003274a60c48c6039f9c85e73ecacb2a94440c4f..d0420ba3c7b93f70daf3041c27f544de016c81a8 100644
--- a/chrome/browser/notifications/notification_display_service.h
+++ b/chrome/browser/notifications/notification_display_service.h
@@ -21,7 +21,6 @@ class Profile;
 // instance can be retrieved through the NotificationDisplayServiceFactory.
 //
 // TODO(peter): Add a NotificationHandler mechanism for registering listeners.
-// TODO(miguelg): Remove the SupportsNotificationCenter method.
 class NotificationDisplayService : public KeyedService {
  public:
   NotificationDisplayService() {}
@@ -40,6 +39,11 @@ class NotificationDisplayService : public KeyedService {
   // notifications and stores them in |*notification_ids| when possible.
   virtual bool GetDisplayed(std::set<std::string>* notifications) const = 0;
 
+  // Async version of the GetDisplayed
+  // TODO(miguelg) Remove the sync version once all paths have been migrated.
+  virtual void GetDisplayedAsync(
+      const NotificationCommon::NotificationResultCallback& callback) const = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(NotificationDisplayService);
 };