Convert drive::FileWriteHelper to a single function for simplification.

chrome/browser/chromeos/drive/file_write_helper.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 CHROME_BROWSER_CHROMEOS_DRIVE_FILE_WRITE_HELPER_H_
-#define CHROME_BROWSER_CHROMEOS_DRIVE_FILE_WRITE_HELPER_H_
-
-#include "base/callback_forward.h"
-#include "base/memory/weak_ptr.h"
-#include "chrome/browser/chromeos/drive/file_errors.h"
-
-namespace base {
-class FilePath;
-}
-
-namespace drive {
-
-class FileSystemInterface;
-
-// This class provides higher level operations for writing to Drive files over
-// FileSystemInterface.
-class FileWriteHelper {
- public:
-  // Callback for PrepareWritableFileAndRun.
-  typedef base::Callback<void(FileError error,
-                              const base::FilePath& file_path)>
-      OpenFileCallback;
-
-  explicit FileWriteHelper(FileSystemInterface* file_system);
-  ~FileWriteHelper();
-
-  // Prepares a local temporary file path and passes it to |callback| on the
-  // blocking thread pool that allows file operations. The modification to
-  // the file is reflected to GData |path|. If |path| does not exist, a new
-  // file is created.
-  //
-  // Must be called from UI thread.
-  void PrepareWritableFileAndRun(const base::FilePath& path,
-                                 const OpenFileCallback& callback);
-
- private:
-  // Part of PrepareWritableFilePathAndRun(). It tries CreateFile for the case
-  // file does not exist yet, does OpenFile to download and mark the file as
-  // dirty, runs |callback|, and finally closes the file.
-  void PrepareWritableFileAndRunAfterOpenFile(
-      const base::FilePath& file_path,
-      const OpenFileCallback& callback,
-      FileError result,
-      const base::FilePath& local_cache_path,
-      const base::Closure& close_callback);
-
-  FileSystemInterface* file_system_;  // Owned by DriveIntegrationService.
-
-  // WeakPtrFactory bound to the UI thread.
-  // Note: This should remain the last member so it'll be destroyed and
-  // invalidate its weak pointers before any other members are destroyed.
-  base::WeakPtrFactory<FileWriteHelper> weak_ptr_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(FileWriteHelper);
-};
-
-}  // namespace drive
-
-#endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILE_WRITE_HELPER_H_