Second patch in making destructors of refcounted objects private.

net/base/test_completion_callback_unittest.cc

Index: net/base/test_completion_callback_unittest.cc
===================================================================
--- net/base/test_completion_callback_unittest.cc	(revision 31079)
+++ net/base/test_completion_callback_unittest.cc	(working copy)
@@ -47,6 +47,10 @@
   void DoWork();
   void DoCallback();
  private:
+  friend class base::RefCountedThreadSafe<ExampleWorker>;
+
+  ~ExampleWorker() {}
+
   // Only used on the origin thread (where DoSomething was called).
   ExampleEmployer* employer_;
   CompletionCallback* callback_;