Make GetDisplayedNotifications asynchronous.

content/shell/browser/layout_test/layout_test_notification_manager.h

 // Copyright 2014 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.
 
 #ifndef CONTENT_SHELL_BROWSER_LAYOUT_TEST_LAYOUT_TEST_NOTIFICATION_MANAGER_H_
 #define CONTENT_SHELL_BROWSER_LAYOUT_TEST_LAYOUT_TEST_NOTIFICATION_MANAGER_H_
 
 #include <stdint.h>
 #include <string>
 #include <unordered_map>
@@ skipping 53 matching lines @@
       base::Closure* cancel_callback) override;
   void DisplayPersistentNotification(
       BrowserContext* browser_context,
       const std::string& notification_id,
       const GURL& service_worker_scope,
       const GURL& origin,
       const PlatformNotificationData& notification_data,
       const NotificationResources& notification_resources) override;
   void ClosePersistentNotification(BrowserContext* browser_context,
                                    const std::string& notification_id) override;
-  bool GetDisplayedNotifications(
+  void GetDisplayedNotifications(
       BrowserContext* browser_context,
-      std::set<std::string>* displayed_notifications) override;
+      const DisplayedNotificationsCallback& callback) override;
 
  private:
   // Structure to represent the information of a persistent notification.
   struct PersistentNotification {
     BrowserContext* browser_context = nullptr;
     GURL origin;
   };
 
   // Closes the notification titled |title|. Must be called on the UI thread.
   void Close(const std::string& title);
@@ skipping 15 matching lines @@
   std::unordered_map<std::string, std::string> notification_id_map_;
 
   base::WeakPtrFactory<LayoutTestNotificationManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(LayoutTestNotificationManager);
 };
 
 }  // content
 
 #endif  // CONTENT_SHELL_BROWSER_LAYOUT_TEST_LAYOUT_TEST_NOTIFICATION_MANAGER_H_