Refactor the UpdateEngine and its actions in the component updater.

components/update_client/ping_manager.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_UPDATE_CLIENT_PING_MANAGER_H_
 #define COMPONENTS_UPDATE_CLIENT_PING_MANAGER_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/threading/thread_checker.h"
 
 namespace update_client {
 
 class Configurator;
-struct CrxUpdateItem;
+class Component;
 
 // Sends fire-and-forget pings.
 class PingManager {
  public:
   explicit PingManager(const scoped_refptr<Configurator>& config);
   virtual ~PingManager();
 
   // Sends a fire and forget ping for the |item|. Returns true if the
   // ping is queued up and may be sent in the future, or false, if an error
   // occurs right away. The ping itself is not persisted and it will be
   // discarded if it can't be sent for any reason.
-  virtual bool SendPing(const CrxUpdateItem* item);
+  virtual bool SendPing(const Component& component);
 
  private:
+  base::ThreadChecker thread_checker_;
+
   const scoped_refptr<Configurator> config_;
 
   DISALLOW_COPY_AND_ASSIGN(PingManager);
 };
 
 }  // namespace update_client
 
 #endif  // COMPONENTS_UPDATE_CLIENT_PING_MANAGER_H_