Make the UI an observer of downloads.

android_webview/native/aw_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 ANDROID_WEBVIEW_NATIVE_AW_WEB_CONTENTS_DELEGATE_H_
 #define ANDROID_WEBVIEW_NATIVE_AW_WEB_CONTENTS_DELEGATE_H_
 
 #include <jni.h>
 
 #include "components/web_contents_delegate_android/web_contents_delegate_android.h"
@@ skipping 12 matching lines @@
       OVERRIDE;
   virtual void FindReply(content::WebContents* web_contents,
                          int request_id,
                          int number_of_matches,
                          const gfx::Rect& selection_rect,
                          int active_match_ordinal,
                          bool final_update) 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 AddNewContents(content::WebContents* source,
                               content::WebContents* new_contents,
                               WindowOpenDisposition disposition,
                               const gfx::Rect& initial_pos,
                               bool user_gesture,
                               bool* was_blocked) OVERRIDE;
   virtual void CloseContents(content::WebContents* source) OVERRIDE;
   virtual void ActivateContents(content::WebContents* contents) OVERRIDE;
 };
 
 bool RegisterAwWebContentsDelegate(JNIEnv* env);
 
 }  // namespace android_webview
 
 #endif  // ANDROID_WEBVIEW_NATIVE_AW_WEB_CONTENTS_DELEGATE_H_