RefCounted types should not have public destructors, chrome/ remaining parts

chrome/service/cloud_print/cloud_print_proxy_backend.cc

Index: chrome/service/cloud_print/cloud_print_proxy_backend.cc
diff --git a/chrome/service/cloud_print/cloud_print_proxy_backend.cc b/chrome/service/cloud_print/cloud_print_proxy_backend.cc
index 21c5c0064866b59a0b78629fedecacaee4cb44e9..40eb68e593becc749e6b10d9bef3ce8f6d0996a3 100644
--- a/chrome/service/cloud_print/cloud_print_proxy_backend.cc
+++ b/chrome/service/cloud_print/cloud_print_proxy_backend.cc
@@ -93,6 +93,10 @@ class CloudPrintProxyBackend::Core
   virtual void OnOutgoingNotification();
 
  private:
+  friend class base::RefCountedThreadSafe<Core>;
+
+  virtual ~Core() {}
+
   // NotifyXXX is how the Core communicates with the frontend across
   // threads.
   void NotifyPrinterListAvailable(