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

content/browser/download/base_file.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_BASE_FILE_H_
 #define CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_
 
 #include <string>
 
 #include "base/file_path.h"
@@ skipping 11 matching lines @@
 class SecureHash;
 }
 namespace net {
 class FileStream;
 }
 
 // File being downloaded and saved to disk. This is a base class
 // for DownloadFile and SaveFile, which keep more state information.
 class CONTENT_EXPORT BaseFile {
  public:
-  BaseFile(const FilePath& full_path,
+  // Either |download_directory| or |full_path| should be non-empty. If
+  // |full_path| isn't specified, a temporary file will be created under
+  // |download_directory|.
+  BaseFile(const FilePath& download_directory,
+           const FilePath& full_path,
            const GURL& source_url,
            const GURL& referrer_url,
            int64 received_bytes,
            bool calculate_hash,
            const std::string& hash_state,
            const linked_ptr<net::FileStream>& file_stream,
            const net::BoundNetLog& bound_net_log);
   virtual ~BaseFile();
 
   // Returns net::OK on success, or a network error code on failure.
@@ skipping 58 matching lines @@
   int64 CurrentSpeedAtTime(base::TimeTicks current_time) const;
 
   // Resets the current state of the hash to the contents of |hash_state_bytes|.
   virtual bool SetHashState(const std::string& hash_state_bytes);
 
   net::Error ClearStream(net::Error error);
 
   static const size_t kSha256HashLen = 32;
   static const unsigned char kEmptySha256Hash[kSha256HashLen];
 
+  // Default download directory to use for temporary file
+  FilePath download_directory_;

[Randy Smith (Not in Mondays), 2012/09/14 16:38:16]

I'm tempted to suggest that instead of doing this we switch the full_path_ into
"directory_" and "name_", and create the temp file in directory_ if name_ is
null.  They're both ugly, but that seems a little more flexible.  Why should
BaseFile have knowledge of the download_directory_?

[asanka, 2012/09/14 19:11:45]

I added a parameter to Initialize() instead and called it default_directory.

+
   // Source URL for the file being downloaded.
   GURL source_url_;
 
   // The URL where the download was initiated.
   GURL referrer_url_;
 
   // OS file stream for writing
   linked_ptr<net::FileStream> file_stream_;
 
   // Amount of data received up so far, in bytes.
@@ skipping 14 matching lines @@
   // Indicates that this class no longer owns the associated file, and so
   // won't delete it on destruction.
   bool detached_;
 
   net::BoundNetLog bound_net_log_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseFile);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_