Make //content responsible for generating notification Ids

content/public/browser/notification_database_data.h

Index: content/public/browser/notification_database_data.h
diff --git a/content/public/browser/notification_database_data.h b/content/public/browser/notification_database_data.h
index e10f3146925cf6b0228b48c90197b28a9a49f117..872bc45c3f91d4d5ae345fbb94e1440a34e031a1 100644
--- a/content/public/browser/notification_database_data.h
+++ b/content/public/browser/notification_database_data.h
@@ -6,7 +6,9 @@
 #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"
 
@@ -15,9 +17,13 @@ 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;