Make the UI an observer of downloads.

chrome/browser/android/chrome_web_contents_delegate_android.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 CHROME_BROWSER_ANDROID_CHROME_WEB_CONTENTS_DELEGATE_ANDROID_H_
 #define CHROME_BROWSER_ANDROID_CHROME_WEB_CONTENTS_DELEGATE_ANDROID_H_
 
 #include <jni.h>
 
 #include "base/files/file_path.h"
@@ skipping 39 matching lines @@
                          bool final_update) OVERRIDE;
   virtual void FindMatchRectsReply(content::WebContents* web_contents,
                                    int version,
                                    const std::vector<gfx::RectF>& rects,
                                    const gfx::RectF& active_rect) OVERRIDE;
   virtual content::JavaScriptDialogManager*
   GetJavaScriptDialogManager() OVERRIDE;
   virtual bool CanDownload(content::RenderViewHost* source,
                            int request_id,
                            const std::string& request_method) OVERRIDE;
-  virtual void OnStartDownload(content::WebContents* source,
-                               content::DownloadItem* download) OVERRIDE;
   virtual void DidNavigateToPendingEntry(content::WebContents* source) OVERRIDE;
   virtual void DidNavigateMainFramePostCommit(
       content::WebContents* source) OVERRIDE;
   virtual void RequestMediaAccessPermission(
       content::WebContents* web_contents,
       const content::MediaStreamRequest& request,
       const content::MediaResponseCallback& callback) OVERRIDE;
   virtual bool RequestPpapiBrokerPermission(
       content::WebContents* web_contents,
       const GURL& url,
@@ skipping 14 matching lines @@
   base::TimeTicks navigation_start_time_;
 };
 
 // Register the native methods through JNI.
 bool RegisterChromeWebContentsDelegateAndroid(JNIEnv* env);
 
 }  // namespace android
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_ANDROID_CHROME_WEB_CONTENTS_DELEGATE_ANDROID_H_