Bug 1035394 - Fix dangerous public destructors in storage - r=bent

storage/test/test_AsXXX_helpers.cpp

@@ -20,6 +20,8 @@ public:
   NS_DECL_ISUPPORTS
   NS_DECL_ASYNCSTATEMENTSPINNER
   Spinner() {}
+protected:
+  virtual ~Spinner() {}
 };
 
 NS_IMPL_ISUPPORTS_INHERITED0(Spinner,