Implement support for fallback update check urls in the component updater

components/component_updater/update_checker.h

 // Copyright 2014 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 COMPONENTS_COMPONENT_UPDATER_UPDATE_CHECKER_H_
 #define COMPONENTS_COMPONENT_UPDATER_UPDATE_CHECKER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "components/component_updater/update_response.h"
+#include "url/gurl.h"
 
 class GURL;
 
 namespace net {
 class URLRequestContextGetter;
 }
 
 namespace component_updater {
 
 class Configurator;
 struct CrxUpdateItem;
 
 class UpdateChecker {
  public:
-  typedef base::Callback<void(int error,
+  typedef base::Callback<void(const GURL& original_url,
+                              int error,
                               const std::string& error_message,
                               const UpdateResponse::Results& results)>
       UpdateCheckCallback;
 
   virtual ~UpdateChecker() {}
 
   // Initiates an update check for the |items_to_check|. |additional_attributes|
   // provides a way to customize the <request> element. This value is inserted
   // as-is, therefore it must be well-formed as an XML attribute string.
   virtual bool CheckForUpdates(
       const std::vector<CrxUpdateItem*>& items_to_check,
-      const std::string& additional_attributes) = 0;
+      const std::string& additional_attributes,
+      const UpdateCheckCallback& update_check_callback) = 0;
 
-  static scoped_ptr<UpdateChecker> Create(
-      const Configurator& config,
-      const UpdateCheckCallback& update_check_callback);
+  static scoped_ptr<UpdateChecker> Create(const Configurator& config);
 
  protected:
   UpdateChecker() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(UpdateChecker);
 };
 
 }  // namespace component_updater
 
 #endif  // COMPONENTS_COMPONENT_UPDATER_UPDATE_CHECKER_H_