Use the user's preferred downloads directory for creating the initial download file.

content/browser/download/download_file_impl.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 CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_IMPL_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_IMPL_H_
 
 #include "content/browser/download/download_file.h"
 
 #include "base/memory/ref_counted.h"
@@ skipping 66 matching lines @@
   // The stream through which data comes.
   // TODO(rdsmith): Move this into BaseFile; requires using the same
   // stream semantics in SavePackage.  Alternatively, replace SaveFile
   // with DownloadFile and get rid of BaseFile.
   scoped_ptr<content::ByteStreamReader> stream_reader_;
 
   // The unique identifier for this download, assigned at creation by
   // the DownloadFileManager for its internal record keeping.
   content::DownloadId id_;
 
+  // The default directory for creating the download file.
+  FilePath default_download_directory_;
+
   // Used to trigger progress updates.
   scoped_ptr<base::RepeatingTimer<DownloadFileImpl> > update_timer_;
 
   // The handle to the request information.  Used for operations outside the
   // download system, specifically canceling a download.
   scoped_ptr<DownloadRequestHandleInterface> request_handle_;
 
   // DownloadManager this download belongs to.
   scoped_refptr<content::DownloadManager> download_manager_;
 
   // Statistics
   size_t bytes_seen_;
   base::TimeDelta disk_writes_time_;
   base::TimeTicks download_start_;
 
   net::BoundNetLog bound_net_log_;
 
   base::WeakPtrFactory<DownloadFileImpl> weak_factory_;
 
   // RAII handle to keep the system from sleeping while we're downloading.
   scoped_ptr<content::PowerSaveBlocker> power_save_blocker_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadFileImpl);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_IMPL_H_