Drop the const modifier on NotificationDisplayService::GetDisplayed

chrome/browser/notifications/message_center_display_service.cc

 // Copyright 2016 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 <set>
 #include <string>
 
 #include "chrome/browser/notifications/message_center_display_service.h"
 
 #include "chrome/browser/notifications/notification.h"
@@ skipping 19 matching lines @@
 }
 
 void MessageCenterDisplayService::Close(
     NotificationCommon::Type notification_type,
     const std::string& notification_id) {
   ui_manager_->CancelById(notification_id,
                           NotificationUIManager::GetProfileID(profile_));
 }
 
 void MessageCenterDisplayService::GetDisplayed(
-    const DisplayedNotificationsCallback& callback) const {
+    const DisplayedNotificationsCallback& callback) {
   auto displayed_notifications =
       base::MakeUnique<std::set<std::string>>(ui_manager_->GetAllIdsByProfile(
           NotificationUIManager::GetProfileID(profile_)));
 
   content::BrowserThread::PostTask(
       content::BrowserThread::UI, FROM_HERE,
       base::Bind(callback, base::Passed(&displayed_notifications),
                  true /* supports_synchronization */));
 }