Fix crash due to VisibilityTimerTabHelper not being cancelled

chrome/browser/notifications/notification_permission_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 CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_PERMISSION_CONTEXT_H_
 #define CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_PERMISSION_CONTEXT_H_
 
 #include "base/gtest_prod_util.h"
 #include "chrome/browser/permissions/permission_context_base.h"
 #include "components/content_settings/core/common/content_settings.h"
 
 class GURL;
 class Profile;
 
 class NotificationPermissionContext : public PermissionContextBase {
  public:
   explicit NotificationPermissionContext(Profile* profile);
   ~NotificationPermissionContext() override;
 
   // PermissionContextBase implementation.
   void ResetPermission(const GURL& requesting_origin,
                        const GURL& embedder_origin) override;
+  void CancelPermissionRequest(content::WebContents* web_contents,
+                               const PermissionRequestID& id) override;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(NotificationPermissionContextTest,
                            IgnoresEmbedderOrigin);
   FRIEND_TEST_ALL_PREFIXES(NotificationPermissionContextTest,
                            NoSecureOriginRequirement);
 
   // PermissionContextBase implementation.
   void DecidePermission(content::WebContents* web_contents,
                         const PermissionRequestID& id,
                         const GURL& requesting_origin,
                         const GURL& embedding_origin,
                         bool user_gesture,
                         const BrowserPermissionCallback& callback) override;
   void UpdateContentSetting(const GURL& requesting_origin,
                             const GURL& embedder_origin,
                             ContentSetting content_setting) override;
   bool IsRestrictedToSecureOrigins() const override;
 
   base::WeakPtrFactory<NotificationPermissionContext> weak_factory_ui_thread_;
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_PERMISSION_CONTEXT_H_