When the download folder does not exist, change the download folder to a user's "Downloads"

chrome/browser/download/download_file_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 DownloadFileManager owns a set of DownloadFile objects, each of which
 // represent one in progress download and performs the disk IO for that
 // download. The DownloadFileManager itself is a singleton object owned by the
 // ResourceDispatcherHost.
 //
 // The DownloadFileManager uses the file_thread for performing file write
@@ skipping 122 matching lines @@
   void StopUpdateTimer();
   void UpdateInProgressDownloads();
 
   // Clean up helper that runs on the download thread.
   void OnShutdown();
 
   // Creates DownloadFile on FILE thread and continues starting the download
   // process.
   void CreateDownloadFile(DownloadCreateInfo* info,
                           DownloadManager* download_manager,
-                          bool hash_needed);
+                          bool hash_needed,
+                          const FilePath& default_download_dir);
 
   // Called only on the download thread.
   DownloadFile* GetDownloadFile(int id);
 
   // Called only from RenameInProgressDownloadFile and
   // RenameCompletingDownloadFile on the FILE thread.
   void CancelDownloadOnRename(int id);
 
   // Erases the download file with the given the download |id| and removes
   // it from the maps.
@@ skipping 10 matching lines @@
   // Schedule periodic updates of the download progress. This timer
   // is controlled from the FILE thread, and posts updates to the UI thread.
   base::RepeatingTimer<DownloadFileManager> update_timer_;
 
   ResourceDispatcherHost* resource_dispatcher_host_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadFileManager);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_FILE_MANAGER_H_