Create and remove sync nodes whenever preferences flip their managed flag

chrome/browser/sync/glue/preference_change_processor.h

 // Copyright (c) 2009 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_SYNC_GLUE_PREFERENCE_CHANGE_PROCESSOR_H_
 #define CHROME_BROWSER_SYNC_GLUE_PREFERENCE_CHANGE_PROCESSOR_H_
 #pragma once
 
 #include <string>
 
@@ skipping 40 matching lines @@
 
   void StartObserving();
   void StopObserving();
 
   // The model we are processing changes from. Non-NULL when |running_| is true.
   PrefService* pref_service_;
 
   // The two models should be associated according to this ModelAssociator.
   PreferenceModelAssociator* model_associator_;
 
+  // Whether we are currently processing a preference change notification.
+  bool processing_pref_change_;
+
   DISALLOW_COPY_AND_ASSIGN(PreferenceChangeProcessor);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_PREFERENCE_CHANGE_PROCESSOR_H_