Update from https://crrev.com/333737

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 147 matching lines @@
       PrefRegistry* pref_registry,
       base::Callback<void(PersistentPrefStore::PrefReadError)>
           read_error_callback,
       bool async);
   virtual ~PrefService();
 
   // Lands pending writes to disk. This should only be used if we need to save
   // immediately (basically, during shutdown).
   void CommitPendingWrite();
 
+  // Schedule a write if there is any lossy data pending. Unlike
+  // CommitPendingWrite() this does not immediately sync to disk, instead it
+  // triggers an eventual write if there is lossy data pending and if there
+  // isn't one scheduled already.
+  void SchedulePendingLossyWrites();
+
   // Returns true if the preference for the given preference name is available
   // and is managed.
   bool IsManagedPreference(const std::string& pref_name) const;
 
   // Returns true if the preference for the given preference name is available
   // and is controlled by the parent/guardian of the child Account.
   bool IsPreferenceManagedByCustodian(const std::string& pref_name) const;
 
   // Returns |true| if a preference with the given name is available and its
   // value can be changed by the user.
@@ skipping 189 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_