Drop the const modifier on NotificationDisplayService::GetDisplayed

chrome/browser/notifications/stub_notification_display_service.h

 // Copyright 2017 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_STUB_NOTIFICATION_DISPLAY_SERVICE_H_
 #define CHROME_BROWSER_NOTIFICATIONS_STUB_NOTIFICATION_DISPLAY_SERVICE_H_
 
 #include <memory>
 #include <utility>
 #include <vector>
@@ skipping 24 matching lines @@
   // Removes all notifications shown by this display service.
   void RemoveAllNotifications(NotificationCommon::Type notification_type,
                               bool by_user);
 
   // NotificationDisplayService implementation:
   void Display(NotificationCommon::Type notification_type,
                const std::string& notification_id,
                const Notification& notification) override;
   void Close(NotificationCommon::Type notification_type,
              const std::string& notification_id) override;
-  void GetDisplayed(
-      const DisplayedNotificationsCallback& callback) const override;
+  void GetDisplayed(const DisplayedNotificationsCallback& callback) override;
 
  private:
   // Data to store for a notification that's being shown through this service.
   using NotificationData = std::pair<NotificationCommon::Type, Notification>;
 
   std::vector<NotificationData> notifications_;
 
   DISALLOW_COPY_AND_ASSIGN(StubNotificationDisplayService);
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_STUB_NOTIFICATION_DISPLAY_SERVICE_H_