--- a/xpcom/io/FileDescriptorFile.cpp
+++ b/xpcom/io/FileDescriptorFile.cpp
@@ -151,16 +151,22 @@ FileDescriptorFile::GetParent(nsIFile** 
 }
 
 NS_IMETHODIMP
 FileDescriptorFile::GetFollowLinks(bool* aFollowLinks)
 {
   return mFile->GetFollowLinks(aFollowLinks);
 }
 
+NS_IMETHODIMP
+FileDescriptorFile::GetPersistentDescriptor(nsACString& aPersistentDescriptor)
+{
+  return mFile->GetPersistentDescriptor(aPersistentDescriptor);
+}
+
 //-----------------------------------------------------------------------------
 // FileDescriptorFile::nsIFile functions that are not currently supported
 //-----------------------------------------------------------------------------
 
 nsresult
 FileDescriptorFile::Append(const nsAString& aNode)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
@@ -228,22 +234,16 @@ FileDescriptorFile::AppendRelativePath(c
 
 NS_IMETHODIMP
 FileDescriptorFile::AppendRelativeNativePath(const nsACString& aFragment)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
-FileDescriptorFile::GetPersistentDescriptor(nsACString& aPersistentDescriptor)
-{
-  return NS_ERROR_NOT_IMPLEMENTED;
-}
-
-NS_IMETHODIMP
 FileDescriptorFile::SetPersistentDescriptor(const nsACString& aPersistentDescriptor)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
 FileDescriptorFile::GetRelativeDescriptor(nsIFile* aFromFile,
                                           nsACString& aRetVal)