Standardize usage of virtual/override/final in chrome/browser/download/

chrome/browser/download/download_history.cc

 // Copyright (c) 2012 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.
 
 // DownloadHistory manages persisting DownloadItems to the history service by
 // observing a single DownloadManager and all its DownloadItems using an
 // AllDownloadItemNotifier.
 //
 // DownloadHistory decides whether and when to add items to, remove items from,
 // and update items in the database. DownloadHistory uses DownloadHistoryData to
@@ skipping 57 matching lines @@
     return (data == NULL) ? NULL
                           : static_cast<const DownloadHistoryData*>(data);
   }
 
   explicit DownloadHistoryData(content::DownloadItem* item)
       : state_(NOT_PERSISTED),
         was_restored_from_history_(false) {
     item->SetUserData(kKey, this);
   }
 
-  virtual ~DownloadHistoryData() {
-  }
+  ~DownloadHistoryData() override {}
 
   PersistenceState state() const { return state_; }
   void SetState(PersistenceState s) { state_ = s; }
 
   bool was_restored_from_history() const { return was_restored_from_history_; }
   void set_was_restored_from_history(bool value) {
     was_restored_from_history_ = value;
   }
 
   // This allows DownloadHistory::OnDownloadUpdated() to see what changed in a
@@ skipping 366 matching lines @@
   removing_ids_.insert(download_id);
 }
 
 void DownloadHistory::RemoveDownloadsBatch() {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   IdSet remove_ids;
   removing_ids_.swap(remove_ids);
   history_->RemoveDownloads(remove_ids);
   FOR_EACH_OBSERVER(Observer, observers_, OnDownloadsRemoved(remove_ids));
 }