Replace the DownloadFileManager with direct ownership

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:
+  // May be constructed on any thread.  All other routines (including
+  // destruction) must occur on the FILE thread.
   BaseFile(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();
 
@@ skipping 93 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_