Use WeakPtr in VersionUpdaterCros for safety

chrome/browser/ui/webui/help/version_updater_chromeos.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 CHROME_BROWSER_UI_WEBUI_HELP_VERSION_UPDATER_CHROMEOS_H_
 #define CHROME_BROWSER_UI_WEBUI_HELP_VERSION_UPDATER_CHROMEOS_H_
 #pragma once
 
 #include "base/compiler_specific.h"
+#include "base/memory/weak_ptr.h"
 #include "chrome/browser/ui/webui/help/version_updater.h"
 #include "chromeos/dbus/update_engine_client.h"
 
 class VersionUpdaterCros : public VersionUpdater,
                            public chromeos::UpdateEngineClient::Observer {
  public:
   // VersionUpdater implementation.
   virtual void CheckForUpdate(const StatusCallback& callback) OVERRIDE;
   virtual void RelaunchBrowser() const OVERRIDE;
   virtual void SetReleaseChannel(const std::string& channel) OVERRIDE;
@@ skipping 16 matching lines @@
 
   // Callback from UpdateEngineClient::GetReleaseTrack().
   void UpdateSelectedChannel(const std::string& channel);
 
   // Callback used to communicate update status to the client.
   StatusCallback callback_;
 
   // Callback used to communicate current channel to the client.
   ChannelCallback channel_callback_;
 
+  base::WeakPtrFactory<VersionUpdaterCros> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(VersionUpdaterCros);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_HELP_VERSION_UPDATER_CHROMEOS_H_