--- a/netwerk/ipc/RemoteOpenFileChild.cpp
+++ b/netwerk/ipc/RemoteOpenFileChild.cpp
@@ -553,16 +553,22 @@ RemoteOpenFileChild::MoveTo(nsIFile *new
 
 NS_IMETHODIMP
 RemoteOpenFileChild::MoveToNative(nsIFile *newParent, const nsACString &newName)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
+RemoteOpenFileChild::RenameTo(nsIFile *newParentDir, const nsAString &newName)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
 RemoteOpenFileChild::Remove(bool recursive)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
 RemoteOpenFileChild::GetPermissions(uint32_t *aPermissions)
 {

--- a/xpcom/io/nsIFile.idl
+++ b/xpcom/io/nsIFile.idl
@@ -37,17 +37,17 @@ interface nsISimpleEnumerator;
  * All methods with string parameters have two forms.  The preferred
  * form operates on UCS-2 encoded characters strings.  An alternate
  * form operates on characters strings encoded in the "native" charset.
  *
  * A string containing characters encoded in the native charset cannot
  * be safely passed to javascript via xpconnect.  Therefore, the "native
  * methods" are not scriptable.
  */
-[scriptable, uuid(272a5020-64f5-485c-a8c4-44b2882ae0a2), builtinclass]
+[scriptable, uuid(a99a6a06-f90d-4659-8fce-c2f87feb1167), builtinclass]
 interface nsIFile : nsISupports
 {
     /**
      *  Create Types
      *
      *  NORMAL_FILE_TYPE - A normal file.
      *  DIRECTORY_TYPE   - A directory/folder.
      */
@@ -176,16 +176,26 @@ interface nsIFile : nsISupports
      *       This param allows you to specify a new name for
      *       the file to be moved. This param may be empty, in
      *       which case the current leaf name will be used.
      */
     void moveTo(in nsIFile newParentDir, in AString newName);
     [noscript] void moveToNative(in nsIFile newParentDir, in ACString newName);
 
     /**
+     *  renameTo
+     *
+     *  This method is identical to moveTo except that if this file or directory
+     *  is moved to a a different volume, it fails and returns an error
+     *  (NS_ERROR_FILE_ACCESS_DENIED).
+     *  This object will still point to the old location after renaming.
+     */
+    void renameTo(in nsIFile newParentDir, in AString newName);
+
+    /**
      *  This will try to delete this file.  The 'recursive' flag
      *  must be PR_TRUE to delete directories which are not empty.
      *
      *  This will not resolve any symlinks.
      */
     void remove(in boolean recursive);
 
     /**

--- a/xpcom/io/nsLocalFileUnix.cpp
+++ b/xpcom/io/nsLocalFileUnix.cpp
@@ -1995,16 +1995,23 @@ nsLocalFile::CopyToFollowingLinks(nsIFil
 {
     SET_UCS_2ARGS_2(CopyToFollowingLinksNative , newParentDir, newName);
 }
 nsresult  
 nsLocalFile::MoveTo(nsIFile *newParentDir, const nsAString &newName)
 {
     SET_UCS_2ARGS_2(MoveToNative, newParentDir, newName);
 }
+
+NS_IMETHODIMP
+nsLocalFile::RenameTo(nsIFile *newParentDir, const nsAString &newName)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 nsresult
 nsLocalFile::GetTarget(nsAString &_retval)
 {   
     GET_UCS(GetNativeTarget, _retval);
 }
 
 // nsIHashable
 

--- a/xpcom/io/nsLocalFileWin.cpp
+++ b/xpcom/io/nsLocalFileWin.cpp
@@ -2145,16 +2145,21 @@ nsLocalFile::CopyToFollowingLinks(nsIFil
 }
 
 NS_IMETHODIMP
 nsLocalFile::MoveTo(nsIFile *newParentDir, const nsAString &newName)
 {
     return CopyMove(newParentDir, newName, false, true);
 }
 
+NS_IMETHODIMP
+nsLocalFile::RenameTo(nsIFile *newParentDir, const nsAString & newName)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
 
 NS_IMETHODIMP
 nsLocalFile::Load(PRLibrary * *_retval)
 {
     // Check we are correctly initialized.
     CHECK_mWorkingPath();
 
     bool isFile;