Make the UI an observer of downloads.

content/public/browser/web_contents_delegate.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 CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 206 matching lines @@
   virtual void LostCapture() {}
 
   // Notification that |contents| has gained focus.
   virtual void WebContentsFocused(WebContents* contents) {}
 
   // Asks the delegate if the given tab can download.
   virtual bool CanDownload(RenderViewHost* render_view_host,
                            int request_id,
                            const std::string& request_method);
 
-  // Notifies the delegate that a download is starting.
-  virtual void OnStartDownload(WebContents* source, DownloadItem* download) {}
-
   // Return much extra vertical space should be allotted to the
   // render view widget during various animations (e.g. infobar closing).
   // This is used to make painting look smoother.
   virtual int GetExtraRenderViewHeight() const;
 
   // Returns true if the context menu operation was handled by the delegate.
   virtual bool HandleContextMenu(const content::ContextMenuParams& params);
 
   // Opens source view for given WebContents that is navigated to the given
   // page url.
@@ skipping 190 matching lines @@
   // Called when |this| is no longer the WebContentsDelegate for |source|.
   void Detach(WebContents* source);
 
   // The WebContents that this is currently a delegate for.
   std::set<WebContents*> attached_contents_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_