Update from https://crrev.com/329939

base/prefs/pref_service.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.
 
 // This provides a way to access the application's current preferences.
 
 // Chromium settings and storage represent user-selected preferences and
 // information and MUST not be extracted, overwritten or modified except
 // through Chromium defined APIs.
 
@@ skipping 110 matching lines @@
     // Returns true if the user can change the Preference value, which is the
     // case if no higher-priority source than the user store controls the
     // Preference.
     bool IsUserModifiable() const;
 
     // Returns true if an extension can change the Preference value, which is
     // the case if no higher-priority source than the extension store controls
     // the Preference.
     bool IsExtensionModifiable() const;
 
+    // Return the registration flags for this pref as a bitmask of
+    // PrefRegistry::PrefRegistrationFlags.
+    uint32 registration_flags() const { return registration_flags_; }
+
    private:
     friend class PrefService;
 
     PrefValueStore* pref_value_store() const {
       return pref_service_->pref_value_store_.get();
     }
 
     const std::string name_;
 
     const base::Value::Type type_;
 
+    uint32 registration_flags_;
+
     // Reference to the PrefService in which this pref was created.
     const PrefService* pref_service_;
   };
 
   // You may wish to use PrefServiceFactory or one of its subclasses
   // for simplified construction.
   PrefService(
       PrefNotifierImpl* pref_notifier,
       PrefValueStore* pref_value_store,
       PersistentPrefStore* user_prefs,
@@ skipping 148 matching lines @@
 
  private:
   // Hash map expected to be fastest here since it minimises expensive
   // string comparisons. Order is unimportant, and deletions are rare.
   // Confirmed on Android where this speeded Chrome startup by roughly 50ms
   // vs. std::map, and by roughly 180ms vs. std::set of Preference pointers.
   typedef base::hash_map<std::string, Preference> PreferenceMap;
 
   // Give access to ReportUserPrefChanged() and GetMutableUserPref().
   friend class subtle::ScopedUserPrefUpdateBase;
+  friend class PrefServiceTest_WriteablePrefStoreFlags_Test;
 
   // Registration of pref change observers must be done using the
   // PrefChangeRegistrar, which is declared as a friend here to grant it
   // access to the otherwise protected members Add/RemovePrefObserver.
   // PrefMember registers for preferences changes notification directly to
   // avoid the storage overhead of the registrar, so its base class must be
   // declared as a friend, too.
   friend class PrefChangeRegistrar;
   friend class subtle::PrefMemberBase;
 
@@ skipping 40 matching lines @@
 
   // Local cache of registered Preference objects. The pref_registry_
   // is authoritative with respect to what the types and default values
   // of registered preferences are.
   mutable PreferenceMap prefs_map_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefService);
 };
 
 #endif  // BASE_PREFS_PREF_SERVICE_H_