RefCounted types should not have public destructors, printing/ and ui/

printing/backend/print_backend.h

Index: printing/backend/print_backend.h
diff --git a/printing/backend/print_backend.h b/printing/backend/print_backend.h
index 8e28b2de991f515c0815a18073b2a5df50bfcef5..84a9d90fbbabe9dc2584365cd5f456969833fac3 100644
--- a/printing/backend/print_backend.h
+++ b/printing/backend/print_backend.h
@@ -53,8 +53,6 @@ struct PRINTING_EXPORT PrinterCapsAndDefaults {
 class PRINTING_EXPORT PrintBackend
     : public base::RefCountedThreadSafe<PrintBackend> {
  public:
-  virtual ~PrintBackend();
-
   // Enumerates the list of installed local and network printers.
   virtual bool EnumeratePrinters(PrinterList* printer_list) = 0;
 
@@ -78,6 +76,10 @@ class PRINTING_EXPORT PrintBackend
   // Return NULL if no print backend available.
   static scoped_refptr<PrintBackend> CreateInstance(
       const base::DictionaryValue* print_backend_settings);
+
+ protected:
+  friend class base::RefCountedThreadSafe<PrintBackend>;
+  virtual ~PrintBackend();
 };
 
 }  // namespace printing