Update from https://crrev.com/328418

base/files/important_file_writer.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 BASE_FILES_IMPORTANT_FILE_WRITER_H_
 #define BASE_FILES_IMPORTANT_FILE_WRITER_H_
 
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 60 matching lines @@
   ~ImportantFileWriter();
 
   const FilePath& path() const { return path_; }
 
   // Returns true if there is a scheduled write pending which has not yet
   // been started.
   bool HasPendingWrite() const;
 
   // Save |data| to target filename. Does not block. If there is a pending write
   // scheduled by ScheduleWrite, it is cancelled.
-  void WriteNow(const std::string& data);
+  void WriteNow(scoped_ptr<std::string> data);
 
   // Schedule a save to target filename. Data will be serialized and saved
   // to disk after the commit interval. If another ScheduleWrite is issued
   // before that, only one serialization and write to disk will happen, and
   // the most recent |serializer| will be used. This operation does not block.
   // |serializer| should remain valid through the lifetime of
   // ImportantFileWriter.
   void ScheduleWrite(DataSerializer* serializer);
 
   // Serialize data pending to be saved and execute write on backend thread.
   void DoScheduledWrite();
 
   // Registers |on_next_successful_write| to be called once, on the next
   // successful write event. Only one callback can be set at once.
   void RegisterOnNextSuccessfulWriteCallback(
       const base::Closure& on_next_successful_write);
 
   TimeDelta commit_interval() const {
     return commit_interval_;
   }
 
   void set_commit_interval(const TimeDelta& interval) {
     commit_interval_ = interval;
   }
 
  private:
   // Helper method for WriteNow().
-  bool PostWriteTask(const std::string& data);
+  bool PostWriteTask(const Callback<bool()>& task);
 
   // If |result| is true and |on_next_successful_write_| is set, invokes
   // |on_successful_write_| and then resets it; no-ops otherwise.
   void ForwardSuccessfulWrite(bool result);
 
   // Invoked once and then reset on the next successful write event.
   base::Closure on_next_successful_write_;
 
   // Path being written to.
   const FilePath path_;
@@ skipping 11 matching lines @@
   TimeDelta commit_interval_;
 
   WeakPtrFactory<ImportantFileWriter> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ImportantFileWriter);
 };
 
 }  // namespace base
 
 #endif  // BASE_FILES_IMPORTANT_FILE_WRITER_H_