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

chrome/browser/download/save_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.
 //
 // Objects that handle file operations for saving files, on the file thread.
 //
 // The SaveFileManager owns a set of SaveFile objects, each of which connects
 // with a SaveItem object which belongs to one SavePackage and runs on the file
 // thread for saving data in order to avoid disk activity on either network IO
 // thread or the UI thread. It coordinates the notifications from the network
@@ skipping 196 matching lines @@
   // Deletes a specified file on the file thread.
   void OnDeleteDirectoryOrFile(const FilePath& full_path, bool is_dir);
 
   // Notifications sent from the UI thread and run on the IO thread
 
   // Initiates a request for URL to be saved.
   void OnSaveURL(const GURL& url,
                  const GURL& referrer,
                  int render_process_host_id,
                  int render_view_id,
+                 const FilePath& default_download_dir,
                  const content::ResourceContext* context);
   // Handler for a notification sent to the IO thread for generating save id.
   void OnRequireSaveJobFromOtherSource(SaveFileCreateInfo* info);
   // Call ResourceDispatcherHost's CancelRequest method to execute cancel
   // action in the IO thread.
   void ExecuteCancelSaveRequest(int render_process_id, int request_id);
 
   // Unique ID for the next SaveFile object.
   int next_id_;
 
@@ skipping 19 matching lines @@
   // hashmap since it is possible to save same URL in different tab at
   // same time.
   typedef base::hash_map<std::string, SavePackage*> StartingRequestsMap;
   typedef base::hash_map<int, StartingRequestsMap> TabToStartingRequestsMap;
   TabToStartingRequestsMap tab_starting_requests_;
 
   DISALLOW_COPY_AND_ASSIGN(SaveFileManager);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_SAVE_FILE_MANAGER_H__