Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/notification_permission_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_RENDERER_NOTIFICATION_PERMISSION_DISPATCHER_H_
 #define CONTENT_RENDERER_NOTIFICATION_PERMISSION_DISPATCHER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 15 matching lines @@
   explicit NotificationPermissionDispatcher(RenderFrame* render_frame);
   ~NotificationPermissionDispatcher() override;
 
   // Requests permission to display Web Notifications for |origin|. The callback
   // will be invoked when the permission status is available. This class will
   // take ownership of |callback|.
   void RequestPermission(const blink::WebSecurityOrigin& origin,
                          blink::WebNotificationPermissionCallback* callback);
 
  private:
+  // RenderFrameObserver implementation.
+  void OnDestruct() override;
+
   void OnPermissionRequestComplete(
       std::unique_ptr<blink::WebNotificationPermissionCallback> callback,
       blink::mojom::PermissionStatus status);
 
   blink::mojom::PermissionServicePtr permission_service_;
 
   DISALLOW_COPY_AND_ASSIGN(NotificationPermissionDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_NOTIFICATION_PERMISSION_DISPATCHER_H_