The platform notification context should observe the Service Worker Context.

content/public/browser/platform_notification_context.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_PLATFORM_NOTIFICATION_CONTEXT_H_
 #define CONTENT_PUBLIC_BROWSER_PLATFORM_NOTIFICATION_CONTEXT_H_
 
 #include <stdint.h>
 
 #include "base/callback.h"
-#include "base/memory/ref_counted.h"
 
 class GURL;
 
 namespace content {
 
 struct NotificationDatabaseData;
 
 // Represents the storage context for persistent Web Notifications, specific to
 // the storage partition owning the instance. All methods defined in this
 // interface may only be used on the IO thread.
-class PlatformNotificationContext
-    : public base::RefCountedThreadSafe<PlatformNotificationContext> {
+class PlatformNotificationContext {
  public:
   using ReadResultCallback =
       base::Callback<void(bool /* success */,
                           const NotificationDatabaseData&)>;
 
   using WriteResultCallback =
       base::Callback<void(bool /* success */,
                           int64_t /* notification_id */)>;
 
   using DeleteResultCallback = base::Callback<void(bool /* success */)>;
@@ skipping 14 matching lines @@
       const WriteResultCallback& callback) = 0;
 
   // Deletes all data associated with |notification_id| belonging to |origin|
   // from the database. |callback| will be invoked with the success status
   // when the operation has completed.
   virtual void DeleteNotificationData(int64_t notification_id,
                                       const GURL& origin,
                                       const DeleteResultCallback& callback) = 0;
 
  protected:
-  friend class base::RefCountedThreadSafe<PlatformNotificationContext>;
-
   virtual ~PlatformNotificationContext() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_PLATFORM_NOTIFICATION_CONTEXT_H_