Downloads: replace BrowserThread::FILE with task scheduler.

content/browser/download/download_item_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_ITEM_IMPL_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 694 matching lines @@
 
   // Error return from DestinationError or received at Start().  Stored
   // separately from last_reason_ so that we can avoid handling destination
   // errors until after file name determination has occurred.
   DownloadInterruptReason deferred_interrupt_reason_ =
       DOWNLOAD_INTERRUPT_REASON_NONE;
 
   // The following fields describe the current state of the download file.
 
   // DownloadFile associated with this download.  Note that this
-  // pointer may only be used or destroyed on the FILE thread.
+  // pointer may only be used or destroyed on the download sequence.
   // This pointer will be non-null only while the DownloadItem is in
   // the IN_PROGRESS state.
   std::unique_ptr<DownloadFile> download_file_;
 
   // Information about |download_file_|.
   DestinationInfo destination_info_;
 
   // Current speed. Calculated by the DownloadFile.
   int64_t bytes_per_sec_ = 0;
 
@@ skipping 25 matching lines @@
   int64_t received_bytes_at_length_mismatch_ = -1;
 
   base::WeakPtrFactory<DownloadItemImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadItemImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_IMPL_H_