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

content/browser/download/save_file.cc

 // 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.
 
 #include "content/browser/download/save_file.h"
 
 #include "base/logging.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/file_stream.h"
 
 using content::BrowserThread;
 
+// TODO(asanka): SaveFile should use the target directory of the save package as
+//               the default download directory when initializing |file_|.
+//               Unfortunately, as it is, constructors of SaveFile don't always
+//               have access to the SavePackage at this point.
 SaveFile::SaveFile(const SaveFileCreateInfo* info, bool calculate_hash)
     : file_(FilePath(),
             info->url,
             GURL(),
             0,
             calculate_hash,
             "",
             linked_ptr<net::FileStream>(),
             net::BoundNetLog()),
       info_(info) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 
   DCHECK(info);
   DCHECK(info->path.empty());
 }
 
 SaveFile::~SaveFile() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 }
 
 net::Error SaveFile::Initialize() {
-  return file_.Initialize();
+  return file_.Initialize(FilePath());
 }
 
 net::Error SaveFile::AppendDataToFile(const char* data, size_t data_len) {
   return file_.AppendDataToFile(data, data_len);
 }
 
 net::Error SaveFile::Rename(const FilePath& full_path) {
   return file_.Rename(full_path);
 }
 
@@ skipping 25 matching lines @@
   return file_.bytes_so_far();
 }
 
 bool SaveFile::GetHash(std::string* hash) {
   return file_.GetHash(hash);
 }
 
 std::string SaveFile::DebugString() const {
   return file_.DebugString();
 }