Use DownloadItemModel for storing chrome/ specific UI data for DownloadItems.

chrome/browser/ui/browser.cc

 // Copyright 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.
 
 #include "chrome/browser/ui/browser.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <shellapi.h>
 #endif  // defined(OS_WIN)
@@ skipping 1461 matching lines @@
 void Browser::RenderWidgetShowing() {
   window_->DisableInactiveFrame();
 }
 
 int Browser::GetExtraRenderViewHeight() const {
   return window_->GetExtraRenderViewHeight();
 }
 
 void Browser::OnStartDownload(WebContents* source,
                               content::DownloadItem* download) {
-  if (!download_util::ShouldShowInShelf(download))
+  scoped_ptr<DownloadItemModel> download_model(new DownloadItemModel(download));
+  if (!download_model->ShouldShowInShelf())
     return;
 
   WebContents* constrained = GetConstrainingWebContents(source);
   if (constrained != source) {
     // Download in a constrained popup is shown in the tab that opened it.
     constrained->GetDelegate()->OnStartDownload(constrained, download);
     return;
   }
 
   if (!window())
     return;
 
   // GetDownloadShelf creates the download shelf if it was not yet created.
   DownloadShelf* shelf = window()->GetDownloadShelf();
-  shelf->AddDownload(new DownloadItemModel(download));
+  shelf->AddDownload(download_model.release());

[sky, 2012/12/10 18:04:52]

Would be nice to use download_model.Pass() here. Maybe in a future patch?

[asanka, 2012/12/10 18:52:14]

I'll do this in a follow-up CL next.

   // Don't show the animation for "Save file" downloads.
   // For non-theme extensions, we don't show the download animation.
   // Show animation in same window as the download shelf. Download shelf
   // may not be in the same window that initiated the download.
   // Don't show the animation if the selected tab is not visible (i.e. the
   // window is minimized, we're in a unit test, etc.).
   WebContents* shelf_tab = chrome::GetActiveWebContents(shelf->browser());
   if ((download->GetTotalBytes() > 0) &&
       !download_crx_util::IsExtensionDownload(*download) &&
       platform_util::IsVisible(shelf_tab->GetNativeView()) &&
@@ skipping 897 matching lines @@
   if (contents && !allow_js_access) {
     contents->web_contents()->GetController().LoadURL(
         target_url,
         content::Referrer(),
         content::PAGE_TRANSITION_LINK,
         std::string());  // No extra headers.
   }
 
   return contents != NULL;
 }