Drop the const modifier on NotificationDisplayService::GetDisplayed

chrome/browser/notifications/message_center_display_service.h

Index: chrome/browser/notifications/message_center_display_service.h
diff --git a/chrome/browser/notifications/message_center_display_service.h b/chrome/browser/notifications/message_center_display_service.h
index 2dcf0e9c3a797ef617ec08d2835ec5acac059aa9..f4750456c616f779dc2bdeb40181afc6ee1568fa 100644
--- a/chrome/browser/notifications/message_center_display_service.h
+++ b/chrome/browser/notifications/message_center_display_service.h
@@ -27,8 +27,7 @@ class MessageCenterDisplayService : public NotificationDisplayService {
                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:
   Profile* profile_;