Introduce the NotificationIdGenerator in //content.

content/browser/notifications/notification_id_generator.h

Index: content/browser/notifications/notification_id_generator.h
diff --git a/content/browser/notifications/notification_id_generator.h b/content/browser/notifications/notification_id_generator.h
new file mode 100644
index 0000000000000000000000000000000000000000..1376809e9fe51e1b6c97011b1ed142243ff0c712
--- /dev/null
+++ b/content/browser/notifications/notification_id_generator.h
@@ -0,0 +1,68 @@
+// 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_BROWSER_NOTIFICATIONS_NOTIFICATION_ID_GENERATOR_H_
+#define CONTENT_BROWSER_NOTIFICATIONS_NOTIFICATION_ID_GENERATOR_H_
+
+#include <stdint.h>
+#include <string>
+
+#include "content/common/content_export.h"
+
+class GURL;
+
+namespace content {
+
+class BrowserContext;
+
+// Generates deterministic notification ids for Web Notifications.
+//
+// The notification id must be deterministic for a given browser context, origin
+// and tag, when the tag is non-empty, or unique for the given notification when
+// the tag is empty. For non-persistent notifications, the uniqueness will be
+// based on the render process id. For persistent notifications, the generated
+// id will be globally unique for the lifetime of the notification database.
+//
+// Notifications of the same type coming from the same origin and having the

[johnme, 2015/05/29 09:34:57]

"of the same type"? That's not what the code enforces - it generates the same
ids for both persistent and non-persistent if they have the same tag.

[Peter Beverloo, 2015/05/29 12:34:08]

Done.

+// same tag will result in the same notification id being generated. This id may
+// then be used to update the notification in the platform notification service.
+//
+// The notification id will be used by the notification service for determining
+// when to replace notifications, and as the unique identifier when a
+// notification has to be closed programmatically.
+//
+// It is important to note that, for persistent notifications, the generated
+// notification id can outlive the browser process responsible for creating it.
+class CONTENT_EXPORT NotificationIdGenerator {
+ public:
+  NotificationIdGenerator(BrowserContext* browser_context,
+                          int render_process_id);
+  ~NotificationIdGenerator();
+
+  // Generates an id for a persistent notification given the notification's
+  // origin, tag and persistent notification id. The persistent notification id
+  // will have been created by the persistent notification database.
+  std::string GenerateForPersistentNotification(
+      const GURL& origin,
+      const std::string& tag,
+      int64_t persistent_notification_id) const;
+
+  // Generates an id for a non-persistent notification given the notification's
+  // origin, tag and non-persistent notification id. The non-persistent
+  // notification id will have created by the renderer with |render_process_id|.
+  std::string GenerateForNonPersistentNotification(
+      const GURL& origin,
+      const std::string& tag,
+      int non_persistent_notification_id) const;

[johnme, 2015/05/29 09:34:57]

Nit: I still find it a bit weird that you pass in a "notification id" to this
and get back a "notification id" (which might be the same as one obtained
earlier when passing in a different id value, if the tag is the same). Perhaps
we can rename non_persistent_notification_id to
non_persistent_notification_request_id so there's only a single concept of
notification id? And something similar for persistent notifications...

[Peter Beverloo, 2015/05/29 12:34:08]

I'm going to leave it as it is in this patch, since renaming that consistently
would have to be done in a variety of places in either case. Let's discuss next
week in person.

+
+ private:
+  // The NotificationMessageFilter that owns |this| will outlive the context.
+  BrowserContext* browser_context_;
+
+  int render_process_id_;
+};
+
+}  // namespace context
+
+#endif  // CONTENT_BROWSER_NOTIFICATIONS_NOTIFICATION_ID_GENERATOR_H_