Make GetDisplayedNotifications asynchronous.

content/browser/notifications/platform_notification_context_impl.h

Index: content/browser/notifications/platform_notification_context_impl.h
diff --git a/content/browser/notifications/platform_notification_context_impl.h b/content/browser/notifications/platform_notification_context_impl.h
index 2a27522abb35ec30dbf47b7ba0b80531fd9a989b..bae629cb831534f34cbfe4c482daf2be0adc2f57 100644
--- a/content/browser/notifications/platform_notification_context_impl.h
+++ b/content/browser/notifications/platform_notification_context_impl.h
@@ -101,7 +101,12 @@ class CONTENT_EXPORT PlatformNotificationContextImpl
 
   ~PlatformNotificationContextImpl() override;
 
-  void InitializeOnIO();
+  void InitializeOnUI(
+      std::unique_ptr<std::set<std::string>> displayed_notifications,
+      bool notification_synchronization_supported);
+  void InitializeOnIO(
+      std::unique_ptr<std::set<std::string>> displayed_notifications,
+      bool notification_synchronization_supported);
   void ShutdownOnIO();
   void CreateServiceOnIO(
       int render_process_id,
@@ -130,8 +135,18 @@ class CONTENT_EXPORT PlatformNotificationContextImpl
 
   // Updates the database (and the result callback) based on
   // |displayed_notifications|
-  // if |sync_supported|. Called on the IO thread.
-  void SynchronizeDisplayedNotificationsForServiceWorkerRegistration(
+  // if |sync_supported|.
+  void SynchronizeDisplayedNotificationsForServiceWorkerRegistrationOnUI(
+      const GURL& origin,
+      int64_t service_worker_registration_id,
+      const ReadAllResultCallback& callback,
+      std::unique_ptr<std::set<std::string>> displayed_notifications,
+      bool sync_supported);
+
+  // Updates the database (and the result callback) based on
+  // |displayed_notifications|
+  // if |sync_supported|.
+  void SynchronizeDisplayedNotificationsForServiceWorkerRegistrationOnIO(
       const GURL& origin,
       int64_t service_worker_registration_id,
       const ReadAllResultCallback& callback,