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

chrome/browser/chromeos/drive/file_system_util.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_SYSTEM_UTIL_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_UTIL_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 133 matching lines @@
 base::FilePath GetCacheRootPath(Profile* profile);
 
 // Migrates cache files from old "persistent" and "tmp" directories to the new
 // "files" directory (see crbug.com/248905).
 // TODO(hashimoto): Remove this function at some point.
 void MigrateCacheFilesFromOldDirectories(
     const base::FilePath& cache_root_directory);
 
 // Callback type for PrepareWritableFileAndRun.
 typedef base::Callback<void (FileError, const base::FilePath& path)>
-    OpenFileCallback;
+    PrepareWritableFileCallback;
 
 // Invokes |callback| on blocking thread pool, after converting virtual |path|
 // string like "/special/drive/foo.txt" to the concrete local cache file path.
 // After |callback| returns, the written content is synchronized to the server.
 //
-// If |path| is not a Drive path, it is regarded as a local path and no path
-// conversion takes place.
-//
-// Must be called from UI thread.
+// The |path| must be a path under Drive. Must be called from UI thread.
 void PrepareWritableFileAndRun(Profile* profile,
                                const base::FilePath& path,
-                               const OpenFileCallback& callback);
+                               const PrepareWritableFileCallback& callback);
 
 // Ensures the existence of |directory| of '/special/drive/foo'.  This will
 // create |directory| and its ancestors if they don't exist.  |callback| is
 // invoked after making sure that |directory| exists.  |callback| should
 // interpret error codes of either FILE_ERROR_OK or FILE_ERROR_EXISTS as
 // indicating that |directory| now exists.
 //
 // If |directory| is not a Drive path, it won't check the existence and just
 // runs |callback|.
 //
@@ skipping 33 matching lines @@
 std::string ReadResourceIdFromGDocFile(const base::FilePath& file_path);
 
 // Returns the (base-16 encoded) MD5 digest of the file content at |file_path|,
 // or an empty string if an error is found.
 std::string GetMd5Digest(const base::FilePath& file_path);
 
 }  // namespace util
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_UTIL_H_