Refactor the interface for the CrxDownloader to take a callback.

chrome/browser/component_updater/crx_downloader.h

 // Copyright 2013 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_COMPONENT_UPDATER_CRX_DOWNLOADER_H_
 #define CHROME_BROWSER_COMPONENT_UPDATER_CRX_DOWNLOADER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 60 matching lines @@
   // more visibility into how the download has been handled, including
   // specific error codes and download metrics.
   typedef base::Callback<void (const Result& result)> DownloadCallback;
 
   // Factory method to create an instance of this class and build the
   // chain of responsibility. |is_background_download| specifies that a
   // background downloader be used, if the platform supports it.
   static CrxDownloader* Create(
       bool is_background_download,
       net::URLRequestContextGetter* context_getter,
-      scoped_refptr<base::SequencedTaskRunner> task_runner,
-      const DownloadCallback& download_callback);
+      scoped_refptr<base::SequencedTaskRunner> task_runner);
   virtual ~CrxDownloader();
 
   // Starts the download. One instance of the class handles one download only.
   // One instance of CrxDownloader can only be started once, otherwise the
   // behavior is undefined. The callback gets invoked if the download can't
   // be started.
-  void StartDownloadFromUrl(const GURL& url);
-  void StartDownload(const std::vector<GURL>& urls);
+  void StartDownloadFromUrl(const GURL& url,
+                            const DownloadCallback& download_callback);
+  void StartDownload(const std::vector<GURL>& urls,
+                     const DownloadCallback& download_callback);
 
   const std::vector<DownloadMetrics> download_metrics() const;
 
  protected:
-  CrxDownloader(scoped_ptr<CrxDownloader> successor,
-                const DownloadCallback& download_callback);
+  explicit CrxDownloader(scoped_ptr<CrxDownloader> successor);
 
   // Handles the fallback in the case of multiple urls and routing of the
   // download to the following successor in the chain. Derived classes must call
   // this function after each attempt at downloading the urls provided
   // in the StartDownload function.
   // In case of errors, |is_handled| indicates that a server side error has
   // occured for the current url and the url should not be retried down
   // the chain to avoid DDOS of the server. This url will be removed from the
   // list of url and never tried again.
   void OnDownloadComplete(bool is_handled,
@@ skipping 14 matching lines @@
 
   std::vector<DownloadMetrics> download_metrics_;
 
   DISALLOW_COPY_AND_ASSIGN(CrxDownloader);
 };
 
 }  // namespace component_updater
 
 #endif  // CHROME_BROWSER_COMPONENT_UPDATER_CRX_DOWNLOADER_H_