Pref service: enable for user prefs in chrome behind a flag.

components/user_prefs/tracked/pref_hash_filter.h

 // Copyright 2013 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_USER_PREFS_TRACKED_PREF_HASH_FILTER_H_
 #define COMPONENTS_USER_PREFS_TRACKED_PREF_HASH_FILTER_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 146 matching lines @@
   using ChangedPathsMap = std::map<std::string, const TrackedPreference*>;
 
   std::unique_ptr<PrefHashStore> pref_hash_store_;
 
   // A store and contents on which to perform extra validations without
   // triggering resets.
   // Will be null if the platform does not support external validation.
   const base::Optional<StoreContentsPair> external_validation_hash_store_pair_;
 
   // Invoked if a reset occurs in a call to FilterOnLoad.
-  const base::Closure on_reset_on_load_;
+  base::Closure on_reset_on_load_;
 
   TrackedPreferencesMap tracked_paths_;
 
   // The set of all paths whose value has changed since the last call to
   // FilterSerializeData.
   ChangedPathsMap changed_paths_;
 
   // Whether to report the validity of the super MAC at load time (via UMA).
   bool report_super_mac_validity_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefHashFilter);
 };
 
 #endif  // COMPONENTS_PREFS_TRACKED_PREF_HASH_FILTER_H_