Detect removed files and reflect the state in chrome://downloads and the download shelf

chrome/browser/download/download_manager.h

 // Copyright (c) 2011 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.
 //
 // The DownloadManager object manages the process of downloading, including
 // updates to the history system and providing the information for displaying
 // the downloads view in the Destinations tab. There is one DownloadManager per
 // active profile in Chrome.
 //
 // Download observers:
@@ skipping 218 matching lines @@
   // Various factors are considered, such as the type of the file, whether a
   // user action initiated the download, and whether the user has explicitly
   // marked the file type as "auto open".
   bool IsDangerous(const DownloadItem& download,
                    const DownloadStateInfo& state,
                    bool visited_referrer_before);
 
   // Called when the user has validated the download of a dangerous file.
   void DangerousDownloadValidated(DownloadItem* download);
 
+  // Checks whether downloaded files still exist. Updates state of downloads
+  // that refer to removed files. The check runs in the background and may
+  // finish asynchronously after this method returns.
+  void CheckForHistoryFilesRemoval();
+
+  // Checks whether a downloaded file still exists and updates the file's state
+  // if the file is already removed. The check runs in the background and may
+  // finish asynchronously after this method returns.
+  void CheckForFileRemoval(DownloadItem* download_item);
+
   // Callback function after url is checked with safebrowsing service.
   void CheckDownloadUrlDone(int32 download_id, bool is_dangerous_url);
 
   // Callback function after we check whether the referrer URL has been visited
   // before today.
   void CheckVisitedReferrerBeforeDone(int32 download_id,
                                       bool visited_referrer_before);
 
   // Callback function after download file hash is checked with safebrowsing
   // service.
@@ skipping 24 matching lines @@
     // The original profile's download manager.
     DownloadManager* observed_download_manager_;
   };
 
   friend struct BrowserThread::DeleteOnThread<BrowserThread::UI>;
   friend class DeleteTask<DownloadManager>;
   friend class OtherDownloadManagerObserver;
 
   virtual ~DownloadManager();
 
+  // Called on the FILE thread to check the existence of a downloaded file.
+  void CheckForFileRemovalOnFileThread(int64 db_handle, const FilePath& path);
+
+  // Called on the UI thread if the FILE thread detects the removal of
+  // the downloaded file. The UI thread updates the state of the file
+  // and then notifies this update to the file's observer.
+  void OnFileRemovalDetected(int64 db_handle);
+
   // Called on the download thread to check whether the suggested file path
   // exists.  We don't check if the file exists on the UI thread to avoid UI
   // stalls from interacting with the file system.
   void CheckIfSuggestedPathExists(int32 download_id,
                                   DownloadStateInfo state,
                                   const FilePath& default_path);
 
   // Called on the UI thread once the DownloadManager has determined whether the
   // suggested file path exists.
   void OnPathExistenceAvailable(int32 download_id,
@@ skipping 118 matching lines @@
   // The "Save As" dialog box used to ask the user where a file should be
   // saved.
   scoped_refptr<SelectFileDialog> select_file_dialog_;
 
   scoped_ptr<OtherDownloadManagerObserver> other_download_manager_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadManager);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_MANAGER_H_