Implement a RenderFrame-less path for Web Notifications.

content/child/notifications/notification_dispatcher.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_CHILD_NOTIFICATIONS_NOTIFICATION_DISPATCHER_H_
+#define CONTENT_CHILD_NOTIFICATIONS_NOTIFICATION_DISPATCHER_H_
+
+#include <map>
+
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "content/child/child_message_filter.h"
+
+namespace base {
+class MessageLoopProxy;
+}
+
+namespace content {
+
+class ThreadSafeSender;
+
+class NotificationDispatcher : public ChildMessageFilter {
+ public:
+  explicit NotificationDispatcher(ThreadSafeSender* thread_safe_sender);
+
+  // Generates a, process-unique new notification Id mapped to |thread_id|, and
+  // return the notification Id. This method can be called on any thread.
+  int GenerateNotificationId(int thread_id);
+
+ protected:
+  ~NotificationDispatcher() override;
+
+ private:
+  bool ShouldHandleMessage(const IPC::Message& msg);
+
+  // ChildMessageFilter implementation.
+  base::TaskRunner* OverrideTaskRunnerForMessage(const IPC::Message& msg)
+      override;
+  bool OnMessageReceived(const IPC::Message& msg) override;
+
+  scoped_refptr<base::MessageLoopProxy> main_thread_loop_proxy_;
+  scoped_refptr<ThreadSafeSender> thread_safe_sender_;
+
+  typedef std::map<int, int> NotificationIdToThreadId;

[Mike West, 2014/10/24 13:20:18]

Nit: `using NotificationIdToThreadId = ...`.

[Peter Beverloo, 2014/10/24 13:57:35]

Done.

+
+  base::Lock notification_id_map_lock_;
+  NotificationIdToThreadId notification_id_map_;
+  int next_notification_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(NotificationDispatcher);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_CHILD_NOTIFICATIONS_NOTIFICATION_DISPATCHER_H_