Delete unused method FilesystemInterface::IsAbsent.

webrtc/rtc_base/win32filesystem.h

Index: webrtc/rtc_base/win32filesystem.h
diff --git a/webrtc/rtc_base/win32filesystem.h b/webrtc/rtc_base/win32filesystem.h
index 9d420331e52dbbdd428668e3c269e503fd9e799d..0fff15dfe0071c1a5d296177203791336624a9af 100644
--- a/webrtc/rtc_base/win32filesystem.h
+++ b/webrtc/rtc_base/win32filesystem.h
@@ -38,10 +38,6 @@ class Win32Filesystem : public FilesystemInterface {
   // Returns true if a file exists at path
   bool IsFile(const Pathname& path) override;
 
-  // Returns true if pathname refers to no filesystem object, every parent
-  // directory either exists, or is also absent.
-  bool IsAbsent(const Pathname& pathname) override;
-
   // All of the following functions set pathname and return true if successful.
   // Returned paths always include a trailing backslash.
   // If create is true, the path will be recursively created.