Drop the const modifier on NotificationDisplayService::GetDisplayed

chrome/browser/notifications/stub_notification_display_service.cc

 // 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.
 
 #include "chrome/browser/notifications/stub_notification_display_service.h"
 
 #include <algorithm>
 
 #include "base/memory/ptr_util.h"
 
@@ skipping 60 matching lines @@
       std::remove_if(
           notifications_.begin(), notifications_.end(),
           [notification_type, notification_id](const NotificationData& data) {
             return data.first == notification_type &&
                    data.second.delegate_id() == notification_id;
           }),
       notifications_.end());
 }
 
 void StubNotificationDisplayService::GetDisplayed(
-    const DisplayedNotificationsCallback& callback) const {
+    const DisplayedNotificationsCallback& callback) {
   std::unique_ptr<std::set<std::string>> notifications =
       base::MakeUnique<std::set<std::string>>();
 
   for (const auto& notification_data : notifications_)
     notifications->insert(notification_data.second.delegate_id());
 
   callback.Run(std::move(notifications), true /* supports_synchronization */);
 }