Make GetDisplayedNotifications asynchronous.

content/public/browser/platform_notification_service.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_PUBLIC_BROWSER_PLATFORM_NOTIFICATION_SERVICE_H_
 #define CONTENT_PUBLIC_BROWSER_PLATFORM_NOTIFICATION_SERVICE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 15 matching lines @@
 struct PlatformNotificationData;
 class ResourceContext;
 
 // The service using which notifications can be presented to the user. There
 // should be a unique instance of the PlatformNotificationService depending
 // on the browsing context being used.
 class CONTENT_EXPORT PlatformNotificationService {
  public:
   virtual ~PlatformNotificationService() {}
 
+  using DisplayedNotificationsCallback =
+      base::Callback<void(std::unique_ptr<std::set<std::string>>,
+                          bool /* supports synchronization */)>;
+
   // Checks if |origin| has permission to display Web Notifications.
   // This method must only be called on the UI thread.
   virtual blink::mojom::PermissionStatus CheckPermissionOnUIThread(
       BrowserContext* browser_context,
       const GURL& origin,
       int render_process_id) = 0;
 
   // Checks if |origin| has permission to display Web Notifications. This method
   // exists to serve the synchronous IPC required by the Notification.permission
   // JavaScript getter, and should not be used for other purposes. See
@@ skipping 25 matching lines @@
       const GURL& origin,
       const PlatformNotificationData& notification_data,
       const NotificationResources& notification_resources) = 0;
 
   // Closes the persistent notification identified by
   // |persistent_notification_id|. This method must be called on the UI thread.
   virtual void ClosePersistentNotification(
       BrowserContext* browser_context,
       const std::string& notification_id) = 0;
 
-  // Writes the ids of all currently displaying notifications for the
-  // given |browser_context| to |displayed_notifications|. Returns whether the
-  // platform is able to provide such a set.
-  virtual bool GetDisplayedNotifications(
+  // Retrieves the ids of all currently displaying notifications and
+  // posts |callback| with the result.
+  virtual void GetDisplayedNotifications(
       BrowserContext* browser_context,
-      std::set<std::string>* displayed_notifications) = 0;
+      const DisplayedNotificationsCallback& callback) = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_PLATFORM_NOTIFICATION_SERVICE_H_