downloads: add the ability to undo download removal.

chrome/browser/download/download_history.h

 // 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.
 
 #ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_HISTORY_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_HISTORY_H_
 
 #include <set>
 #include <vector>
 
@@ skipping 99 matching lines @@
 
   // AllDownloadItemNotifier::Observer
   void OnDownloadCreated(content::DownloadManager* manager,
                          content::DownloadItem* item) override;
   void OnDownloadUpdated(content::DownloadManager* manager,
                          content::DownloadItem* item) override;
   void OnDownloadOpened(content::DownloadManager* manager,
                         content::DownloadItem* item) override;
   void OnDownloadRemoved(content::DownloadManager* manager,
                          content::DownloadItem* item) override;
+  void OnDownloadRevived(content::DownloadManager* manager,
+                         content::DownloadItem* item) override;
 
   // Schedule a record to be removed from |history_| the next time
   // RemoveDownloadsBatch() runs. Schedule RemoveDownloadsBatch() to be run soon
   // if it isn't already scheduled.
   void ScheduleRemoveDownload(uint32 download_id);
 
   // Removes all |removing_ids_| from |history_|.
   void RemoveDownloadsBatch();
 
   AllDownloadItemNotifier notifier_;
@@ skipping 19 matching lines @@
   int64 history_size_;
 
   ObserverList<Observer> observers_;
 
   base::WeakPtrFactory<DownloadHistory> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadHistory);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_HISTORY_H_