Delete unused methods for replacing the "default filesystem".

Bug: webrtc:6424
Change-Id: I7f76fe71ac395088c3b632e43475933cc13e47cd
Reviewed-on: https://webrtc-review.googlesource.com/83725
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23728}
diff --git a/rtc_base/fileutils.h b/rtc_base/fileutils.h
index fcbc6c3..132fd88 100644
--- a/rtc_base/fileutils.h
+++ b/rtc_base/fileutils.h
@@ -103,46 +103,28 @@
 
 class Filesystem {
  public:
-  static FilesystemInterface* default_filesystem() {
-    RTC_DCHECK(default_filesystem_);
-    return default_filesystem_;
-  }
-
-  static void set_default_filesystem(FilesystemInterface* filesystem) {
-    default_filesystem_ = filesystem;
-  }
-
-  static FilesystemInterface* swap_default_filesystem(
-      FilesystemInterface* filesystem) {
-    FilesystemInterface* cur = default_filesystem_;
-    default_filesystem_ = filesystem;
-    return cur;
-  }
-
   static bool DeleteFile(const Pathname& filename) {
-    return EnsureDefaultFilesystem()->DeleteFile(filename);
+    return GetFilesystem()->DeleteFile(filename);
   }
 
   static bool MoveFile(const Pathname& old_path, const Pathname& new_path) {
-    return EnsureDefaultFilesystem()->MoveFile(old_path, new_path);
+    return GetFilesystem()->MoveFile(old_path, new_path);
   }
 
   static bool IsFolder(const Pathname& pathname) {
-    return EnsureDefaultFilesystem()->IsFolder(pathname);
+    return GetFilesystem()->IsFolder(pathname);
   }
 
   static bool IsFile(const Pathname& pathname) {
-    return EnsureDefaultFilesystem()->IsFile(pathname);
+    return GetFilesystem()->IsFile(pathname);
   }
 
   static bool GetFileSize(const Pathname& path, size_t* size) {
-    return EnsureDefaultFilesystem()->GetFileSize(path, size);
+    return GetFilesystem()->GetFileSize(path, size);
   }
 
  private:
-  static FilesystemInterface* default_filesystem_;
-
-  static FilesystemInterface* EnsureDefaultFilesystem();
+  static FilesystemInterface* GetFilesystem();
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(Filesystem);
 };