Integrate registry_hash_store_contents with the rest of tracked prefs.

components/prefs/json_pref_store.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 COMPONENTS_PREFS_JSON_PREF_STORE_H_
 #define COMPONENTS_PREFS_JSON_PREF_STORE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 234 matching lines @@
 
   std::unique_ptr<ReadErrorDelegate> error_delegate_;
 
   bool initialized_;
   bool filtering_in_progress_;
   bool pending_lossy_write_;
   PrefReadError read_error_;
 
   std::set<std::string> keys_need_empty_value_;
 
-  bool has_pending_successful_write_reply_;
-  bool has_pending_write_callbacks_;
+  bool has_pending_write_reply_ = true;
   base::Closure on_next_successful_write_reply_;
 
   WriteCountHistogram write_count_histogram_;
 
   DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
 };
 
 #endif  // COMPONENTS_PREFS_JSON_PREF_STORE_H_