Make functions in fileutils.h use "const std::string&".

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 40 matching lines @@
 // Where
 // * platform is either of "win", "mac" or "linux".
 // * architecture is either of "32" or "64".
 //
 // Arguments:
 //    name - Name of the resource file. If a plain filename (no directory path)
 //           is supplied, the file is assumed to be located in resources/
 //           If a directory path is prepended to the filename, a subdirectory
 //           hierarchy reflecting that path is assumed to be present.
 //    extension - File extension, without the dot, i.e. "bmp" or "yuv".
-std::string ResourcePath(std::string name, std::string extension);
+std::string ResourcePath(const std::string& name,
+                         const std::string& extension);
 
 // 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(std::string directory_name);
+bool CreateDir(const std::string& directory_name);
 
 // Checks if a file exists.
-bool FileExists(std::string& file_name);
+bool FileExists(const std::string& file_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(std::string filename);
+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_