No need to pass DownloadItemModel ownership.

chrome/browser/ui/cocoa/download/download_shelf_controller.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.
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/memory/scoped_nsobject.h"
 #include "base/memory/scoped_ptr.h"
 #import "chrome/browser/ui/cocoa/view_resizer.h"
 
 @class AnimatableView;
 class Browser;
 @class BrowserWindowController;
 @class DownloadItemController;
-class DownloadItemModel;
 class DownloadShelf;
 @class DownloadShelfView;
 @class HyperlinkButtonCell;
 @class HoverButton;
 
 namespace content {
+class DownloadItem;
 class PageNavigator;
 }
 
 // A controller class that manages the download shelf for one window. It is
 // responsible for the behavior of the shelf itself (showing/hiding, handling
 // the link, layout) as well as for managing the download items it contains.
 //
 // All the files in cocoa/downloads_* are related as follows:
 //
 // download_shelf_mac bridges calls from chromium's c++ world to the objc
@@ skipping 51 matching lines @@
 - (AnimatableView*)animatableView;
 
 - (DownloadShelf*)bridge;
 - (BOOL)isVisible;
 
 - (IBAction)show:(id)sender;
 
 // Run when the user clicks the close button on the right side of the shelf.
 - (IBAction)hide:(id)sender;
 
-- (void)addDownloadItem:(DownloadItemModel*)model;
+- (void)addDownloadItem:(content::DownloadItem*)downloadItem;
 
 // Remove a download, possibly via clearing browser data.
 - (void)remove:(DownloadItemController*)download;
 
 // Called by individual item controllers when their downloads are opened.
 - (void)downloadWasOpened:(DownloadItemController*)download;
 
 // Notification that we are closing and should release our downloads.
 - (void)exiting;
 
 // Return the height of the download shelf.
 - (float)height;
 
 // Re-layouts all download items based on their current state.
 - (void)layoutItems;
 
 @end