Make //content responsible for generating notification Ids

content/public/browser/notification_database_data.h

 // Copyright 2015 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_NOTIFICATION_DATABASE_DATA_H_
 #define CONTENT_PUBLIC_BROWSER_NOTIFICATION_DATABASE_DATA_H_
 
 #include <stdint.h>
+#include <string>
 
+#include "content/common/content_export.h"
 #include "content/public/common/platform_notification_data.h"
 #include "url/gurl.h"
 
 namespace content {
 
 // Stores information about a Web Notification as available in the notification
 // database. Beyond the notification's own data, its id and attribution need
 // to be available for users of the database as well.
-struct NotificationDatabaseData {
-  // Id of the notification as allocated by the NotificationDatabase.
-  int64_t notification_id = 0;
+struct CONTENT_EXPORT NotificationDatabaseData {
+  NotificationDatabaseData();
+  NotificationDatabaseData(const NotificationDatabaseData& other);

[piman, 2016/09/08 17:12:49]

nit: worth adding a move constructor to avoid copying strings (explicit
definition of the copy constructor disables the implicit move constructor that
was there before).

Also, please consider adding copy-assign and move-assign operators
(rule-of-3/rule-of-5, see
http://en.cppreference.com/w/cpp/language/rule_of_three).

[Peter Beverloo, 2016/09/08 18:56:03]

I've added the assignment operator to this class. There is one deliberate copy
of this class now - in future CLs I plan to (a) remove NotificationDatabaseData
from the //content API, and (b) remove the need to copy the data at all.

Would you recommend a pass-by-value paradigm with std::move() (where possible)
over passing it by reference, as we currently do?

+  ~NotificationDatabaseData();
+
+  // Id of the notification as assigned by the NotificationIdGenerator.
+  std::string notification_id;
 
   // Origin of the website this notification is associated with.
   GURL origin;
 
   // Id of the Service Worker registration this notification is associated with.
   int64_t service_worker_registration_id = 0;
 
   // Platform data of the notification that's being stored.
   PlatformNotificationData notification_data;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_NOTIFICATION_DATABASE_DATA_H_