[Chromecast] Remove usage of nonreentrant functions.

chromecast/base/file_utils.h

+// Copyright 2016 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 CHROMECAST_BASE_FILE_UTILS_H_
+#define CHROMECAST_BASE_FILE_UTILS_H_
+
+#include "base/files/file_path.h"
+
+namespace chromecast {
+
+// Lock a file (blocking request) with filepath |path|. Returns the file
+// descriptor on success, an invalid file descriptor (-1) on failure. Failure
+// indicates that |path| does not exist, or the locking procedure failed.
+int OpenAndLockFile(const base::FilePath& path);

[slan, 2016/08/08 16:37:10]

What is the expectation if the file does not exist?

[ameyak, 2016/08/08 18:00:43]

Returns invalid file descriptor (-1)

[slan, 2016/08/08 18:32:19]

Oh, it's right there in the comment. 
https://i.ytimg.com/vi/2hlu0qd1Huc/hqdefault.jpg

+
+// Unlock a file (blocking request) denoted by file descriptor |fd|. Returns
+// true on success, false on failure.
+bool UnlockAndCloseFile(const int fd);
+
+}  // namespace chromecast
+
+#endif  // CHROMECAST_BASE_FILE_UTILS_H_