about:sync: Fix refresh crash and broken node browser

chrome/browser/ui/webui/sync_internals_message_handler.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 CHROME_BROWSER_UI_WEBUI_SYNC_INTERNALS_MESSAGE_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SYNC_INTERNALS_MESSAGE_HANDLER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 48 matching lines @@
   virtual void OnProtocolEvent(const syncer::ProtocolEvent& e) OVERRIDE;
 
  private:
   // Fetches updated aboutInfo and sends it to the page in the form of an
   // onAboutInfoUpdated event.
   void SendAboutInfo();
 
   ProfileSyncService* GetProfileSyncService();
 
   base::WeakPtr<syncer::JsController> js_controller_;
+
+  // A flag used to prevent double-registration with ProfileSyncService.
+  bool is_registered_;
+
   base::WeakPtrFactory<SyncInternalsMessageHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncInternalsMessageHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SYNC_INTERNALS_MESSAGE_HANDLER_H_