Make the UI an observer of downloads.

chrome/browser/android/chrome_web_contents_delegate_android.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 "chrome/browser/android/chrome_web_contents_delegate_android.h"
 
 #include "base/android/jni_android.h"
 #include "chrome/browser/file_select_helper.h"
 #include "chrome/browser/ui/app_modal_dialogs/javascript_dialog_creator.h"
 #include "chrome/browser/ui/find_bar/find_match_rects_details.h"
@@ skipping 232 matching lines @@
     int request_id,
     const std::string& request_method) {
   if (request_method == net::HttpRequestHeaders::kGetMethod) {
     content::DownloadControllerAndroid::Get()->CreateGETDownload(
         source, request_id);
     return false;
   }
   return true;
 }
 
-void ChromeWebContentsDelegateAndroid::OnStartDownload(
-    WebContents* source,
-    content::DownloadItem* download) {
-  content::DownloadControllerAndroid::Get()->OnPostDownloadStarted(
-      source, download);
-}
-
 }  // namespace android
 }  // namespace chrome