No need to pass DownloadItemModel ownership.

chrome/browser/ui/cocoa/download/download_item_mac.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_UI_COCOA_DOWNLOAD_DOWNLOAD_ITEM_MAC_H_
 #define CHROME_BROWSER_UI_COCOA_DOWNLOAD_DOWNLOAD_ITEM_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/memory/scoped_nsobject.h"
 #include "base/memory/scoped_ptr.h"
+#include "chrome/browser/download/download_item_model.h"
 #include "chrome/browser/icon_manager.h"
 #include "chrome/common/cancelable_task_tracker.h"
 #include "content/public/browser/download_item.h"
 #include "content/public/browser/download_manager.h"
 
 @class DownloadItemController;
-class DownloadItemModel;
 
 namespace gfx{
 class Image;
 }
 
 // A class that bridges the visible mac download items to chromium's download
 // model. The owning object (DownloadItemController) must explicitly call
 // |LoadIcon| if it wants to display the icon associated with this download.
 
 class DownloadItemMac : content::DownloadItem::Observer {
  public:
-  // DownloadItemMac takes ownership of |download_model|.
-  DownloadItemMac(DownloadItemModel* download_model,
+  DownloadItemMac(content::DownloadItem* download,
                   DownloadItemController* controller);
 
   // Destructor.
   virtual ~DownloadItemMac();
 
   // content::DownloadItem::Observer implementation
   virtual void OnDownloadUpdated(content::DownloadItem* download) OVERRIDE;
   virtual void OnDownloadOpened(content::DownloadItem* download) OVERRIDE;
   virtual void OnDownloadDestroyed(content::DownloadItem* download) OVERRIDE;
 
-  DownloadItemModel* download_model() { return download_model_.get(); }
+  DownloadItemModel* download_model() { return &download_model_; }
 
   // Asynchronous icon loading support.
   void LoadIcon();
 
  private:
   // Callback for asynchronous icon loading.
   void OnExtractIconComplete(gfx::Image* icon_bitmap);
 
   // The download item model we represent.
-  scoped_ptr<DownloadItemModel> download_model_;
+  DownloadItemModel download_model_;
 
   // The objective-c controller object.
   DownloadItemController* item_controller_;  // weak, owns us.
 
   // For canceling an in progress icon request.
   CancelableTaskTracker cancelable_task_tracker_;
 
   // Stores the last known path where the file will be saved.
   FilePath lastFilePath_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadItemMac);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_DOWNLOAD_DOWNLOAD_ITEM_MAC_H_