Make the UI an observer of downloads.

content/public/browser/download_manager_delegate.cc

 // 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.
 
 #include "content/public/browser/download_manager_delegate.h"
 
 #include "content/public/browser/download_id.h"
 #include "content/public/browser/download_item.h"
 
 namespace content {
 
 DownloadId DownloadManagerDelegate::GetNextId() {
   return DownloadId::Invalid();
 }
 
 bool DownloadManagerDelegate::DetermineDownloadTarget(
     DownloadItem* item,
     const DownloadTargetCallback& callback) {
   return false;
 }
 
-WebContents* DownloadManagerDelegate::
-    GetAlternativeWebContentsToNotifyForDownload() {
-  return NULL;
-}
-
 bool DownloadManagerDelegate::ShouldOpenFileBasedOnExtension(
     const base::FilePath& path) {
   return false;
 }
 
 bool DownloadManagerDelegate::ShouldCompleteDownload(
     DownloadItem* item,
     const base::Closure& callback) {
   return true;
 }
 
 bool DownloadManagerDelegate::ShouldOpenDownload(
     DownloadItem* item, const DownloadOpenDelayedCallback& callback) {
   return true;
 }
 
 bool DownloadManagerDelegate::GenerateFileHash() {
   return false;
 }
 
 DownloadManagerDelegate::~DownloadManagerDelegate() {}
 
 }  // namespace content