Implement support for fallback update check urls in the component updater

components/component_updater/update_checker.h

Index: components/component_updater/update_checker.h
diff --git a/components/component_updater/update_checker.h b/components/component_updater/update_checker.h
index 0e372e4fca99ad34c5edad9de6d03d2744fb2662..1b9498f3b85da8619a95ec0123afecdb793ac444 100644
--- a/components/component_updater/update_checker.h
+++ b/components/component_updater/update_checker.h
@@ -26,7 +26,8 @@ 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;
@@ -38,11 +39,10 @@ class UpdateChecker {
   // 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() {}