Drop the const modifier on NotificationDisplayService::GetDisplayed

chrome/browser/notifications/notification_display_service.h

 // 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.
 
 #ifndef CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_DISPLAY_SERVICE_H_
 #define CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_DISPLAY_SERVICE_H_
 
 #include <memory>
 #include <set>
 #include <string>
@@ skipping 24 matching lines @@
   virtual void Display(NotificationCommon::Type notification_type,
                        const std::string& notification_id,
                        const Notification& notification) = 0;
 
   // Closes the notification identified by |notification_id|.
   virtual void Close(NotificationCommon::Type notification_type,
                      const std::string& notification_id) = 0;
 
   // Writes the ids of all currently displaying notifications and
   // invokes |callback| with the result once known.
-  virtual void GetDisplayed(
-      const DisplayedNotificationsCallback& callback) const = 0;
+  virtual void GetDisplayed(const DisplayedNotificationsCallback& callback) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NotificationDisplayService);
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_DISPLAY_SERVICE_H_