Make the UI an observer of downloads.

chrome/browser/ui/browser.h

Index: chrome/browser/ui/browser.h
diff --git a/chrome/browser/ui/browser.h b/chrome/browser/ui/browser.h
index 735fd9634929b6fc980d6db2e7073dbbf6ebba71..aadbfcf72c4e8bb3e859b9dd4fbb5289482ccdf5 100644
--- a/chrome/browser/ui/browser.h
+++ b/chrome/browser/ui/browser.h
@@ -486,6 +486,9 @@ class Browser : public TabStripModelObserver,
   void MaybeUpdateBookmarkBarStateForInstantPreview(
       const chrome::search::Mode& mode);
 
+  // Show a download on the download shelf.
+  void ShowDownload(content::DownloadItem* download);
+
   FullscreenController* fullscreen_controller() {
     return fullscreen_controller_.get();
   }
@@ -584,8 +587,6 @@ class Browser : public TabStripModelObserver,
   virtual void SetFocusToLocationBar(bool select_all) OVERRIDE;
   virtual void RenderWidgetShowing() OVERRIDE;
   virtual int GetExtraRenderViewHeight() const OVERRIDE;
-  virtual void OnStartDownload(content::WebContents* source,
-                               content::DownloadItem* download) OVERRIDE;
   virtual void ViewSourceForTab(content::WebContents* source,
                                 const GURL& page_url) OVERRIDE;
   virtual void ViewSourceForFrame(