Reduce dependencies on rtc::FileSystem in FileRotatingStream tests, adding helpers in webrtc::test::

webrtc/test/testsupport/fileutils.h

 /*
  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 53 matching lines @@
 // Gets the current working directory for the executing program.
 // Returns "./" if for some reason it is not possible to find the working
 // directory.
 std::string WorkingDir();
 
 // Creates a directory if it not already exists.
 // Returns true if successful. Will print an error message to stderr and return
 // false if a file with the same name already exists.
 bool CreateDir(const std::string& directory_name);
 
+// Removes a directory, which must already be empty.
+bool RemoveDir(const std::string& directory_name);
+
+// Removes a file.
+bool RemoveFile(const std::string& file_name);
+
 // Checks if a file exists.
 bool FileExists(const std::string& file_name);
 
 // Checks if a directory exists.
 bool DirExists(const std::string& directory_name);
 
 // File size of the supplied file in bytes. Will return 0 if the file is
 // empty or if the file does not exist/is readable.
 size_t GetFileSize(const std::string& filename);
 
 // Sets the executable path, i.e. the path to the executable that is being used
 // when launching it. This is usually the path relative to the working directory
 // but can also be an absolute path. The intention with this function is to pass
 // the argv[0] being sent into the main function to make it possible for
 // fileutils.h to find the correct project paths even when the working directory
 // is outside the project tree (which happens in some cases).
 void SetExecutablePath(const std::string& path_to_executable);
 
 }  // namespace test
 }  // namespace webrtc
 
 #endif  // WEBRTC_TEST_TESTSUPPORT_FILEUTILS_H_