No need to pass DownloadItemModel ownership.

chrome/browser/download/download_item_model.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 CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_MODEL_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_MODEL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 17 matching lines @@
 // such, the caller is expected to ensure that the |download| passed into the
 // constructor outlives this |DownloadItemModel|. In addition, multiple
 // DownloadItemModel objects could be wrapping the same DownloadItem.
 class DownloadItemModel {
  public:
   // Constructs a DownloadItemModel. The caller must ensure that |download|
   // outlives this object.
   explicit DownloadItemModel(content::DownloadItem* download);
   ~DownloadItemModel();
 
-  // Cancel the task corresponding to the item.
-  void CancelTask();
-
   // Returns a long descriptive string for a download that's in the INTERRUPTED
   // state. For other downloads, the returned string will be empty.
   string16 GetInterruptReasonText() const;
 
   // Returns a short one-line status string for the download.
   string16 GetStatusText() const;
 
   // Returns a string suitable for use as a tooltip. For a regular download, the
   // tooltip is the filename. For an interrupted download, the string states the
   // filename and a short description of the reason for interruption. For
@@ skipping 54 matching lines @@
 
   // The DownloadItem that this model represents. Note that DownloadItemModel
   // itself shouldn't maintain any state since there can be more than one
   // DownloadItemModel in use with the same DownloadItem.
   content::DownloadItem* download_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadItemModel);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_MODEL_H_