Revert of base: Remove use of MessageLoopProxy

base/files/important_file_writer.cc

 // Copyright (c) 2011 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.
 
 #include "base/files/important_file_writer.h"
 
 #include <stdio.h>
 
 #include <string>
 
@@ skipping 112 matching lines @@
 
 ImportantFileWriter::ImportantFileWriter(
     const FilePath& path,
     const scoped_refptr<base::SequencedTaskRunner>& task_runner)
     : path_(path),
       task_runner_(task_runner),
       serializer_(NULL),
       commit_interval_(TimeDelta::FromMilliseconds(kDefaultCommitIntervalMs)),
       weak_factory_(this) {
   DCHECK(CalledOnValidThread());
-  DCHECK(task_runner_);
+  DCHECK(task_runner_.get());
 }
 
 ImportantFileWriter::~ImportantFileWriter() {
   // We're usually a member variable of some other object, which also tends
   // to be our serializer. It may not be safe to call back to the parent object
   // being destructed.
   DCHECK(!HasPendingWrite());
 }
 
 bool ImportantFileWriter::HasPendingWrite() const {
@@ skipping 73 matching lines @@
 
 void ImportantFileWriter::ForwardSuccessfulWrite(bool result) {
   DCHECK(CalledOnValidThread());
   if (result && !on_next_successful_write_.is_null()) {
     on_next_successful_write_.Run();
     on_next_successful_write_.Reset();
   }
 }
 
 }  // namespace base