Second patch in making destructors of refcounted objects private.

net/base/directory_lister.h

Index: net/base/directory_lister.h
===================================================================
--- net/base/directory_lister.h	(revision 31079)
+++ net/base/directory_lister.h	(working copy)
@@ -35,7 +35,6 @@
   };
 
   DirectoryLister(const FilePath& dir, DirectoryListerDelegate* delegate);
-  ~DirectoryLister();
 
   // Call this method to start the directory enumeration thread.
   bool Start();
@@ -53,8 +52,11 @@
   void ThreadMain();
 
  private:
+  friend class base::RefCountedThreadSafe<DirectoryLister>;
   friend class DirectoryDataEvent;
 
+  ~DirectoryLister();
+
   void OnReceivedData(const file_util::FileEnumerator::FindInfo* data,
                       int count);
   void OnDone(int error);