Revert "Delete rtc::Pathname"

This reverts commit 6b9dec0d16f2df59fa2820c5ec1341be52fb9f32.

Reason for revert: speculative revert for breaking internal projects

Original change's description:
> Delete rtc::Pathname
> 
> Bug: webrtc:6424
> Change-Id: Iec01dc5dd1426d4558983b828b67af872107d723
> Reviewed-on: https://webrtc-review.googlesource.com/c/108400
> Commit-Queue: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#25479}

TBR=kwiberg@webrtc.org,nisse@webrtc.org

Change-Id: I3129a81a1d8e36b3e6c67572410bdc478ec4d5e9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:6424
Reviewed-on: https://webrtc-review.googlesource.com/c/109201
Reviewed-by: Qingsi Wang <qingsi@webrtc.org>
Commit-Queue: Qingsi Wang <qingsi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25490}
diff --git a/rtc_base/unixfilesystem.h b/rtc_base/unixfilesystem.h
index 32af9b5..d95132c 100644
--- a/rtc_base/unixfilesystem.h
+++ b/rtc_base/unixfilesystem.h
@@ -14,6 +14,7 @@
 #include <stddef.h>
 
 #include "rtc_base/fileutils.h"
+#include "rtc_base/pathutils.h"
 
 namespace rtc {
 
@@ -24,18 +25,20 @@
 
   // This will attempt to delete the file located at filename.
   // It will fail with VERIY if you pass it a non-existant file, or a directory.
-  bool DeleteFile(const std::string& filename) override;
+  bool DeleteFile(const Pathname& filename) override;
 
   // This moves a file from old_path to new_path, where "file" can be a plain
   // file or directory, which will be moved recursively.
   // Returns true if function succeeds.
-  bool MoveFile(const std::string& old_path,
-                const std::string& new_path) override;
+  bool MoveFile(const Pathname& old_path, const Pathname& new_path) override;
+
+  // Returns true if a pathname is a directory
+  bool IsFolder(const Pathname& pathname) override;
 
   // Returns true of pathname represents an existing file
-  bool IsFile(const std::string& pathname) override;
+  bool IsFile(const Pathname& pathname) override;
 
-  bool GetFileSize(const std::string& path, size_t* size) override;
+  bool GetFileSize(const Pathname& path, size_t* size) override;
 };
 
 }  // namespace rtc