Pass blocking pool runner to CreateTemporaryFile in SyncFS v2 drive_backend

chrome/browser/sync_file_system/drive_backend/drive_backend_util.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 CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_DRIVE_BACKEND_UTIL_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_DRIVE_BACKEND_UTIL_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 25 matching lines @@
 scoped_ptr<FileMetadata> CreateFileMetadataFromFileResource(
     int64 change_id,
     const google_apis::FileResource& resource);
 scoped_ptr<FileMetadata> CreateFileMetadataFromChangeResource(
     const google_apis::ChangeResource& change);
 scoped_ptr<FileMetadata> CreateDeletedFileMetadata(
     int64 change_id,
     const std::string& file_id);
 
 // Creates a temporary file in |dir_path|.  This must be called on an
-// IO-allowed thread.
-webkit_blob::ScopedFile CreateTemporaryFile();
+// IO-allowed task runner, and the runner must be given as |file_task_runner|.
+webkit_blob::ScopedFile CreateTemporaryFile(
+    base::TaskRunner* file_task_runner);
 
 std::string FileKindToString(FileKind file_kind);
 
 bool HasFileAsParent(const FileDetails& details, const std::string& file_id);
 
 std::string GetMimeTypeFromTitle(const base::FilePath& title);
 
 scoped_ptr<google_apis::ResourceEntry> GetOldestCreatedFolderResource(
     ScopedVector<google_apis::ResourceEntry> list);
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_DRIVE_BACKEND_UTIL_H_