RefCounted types should not have public destructors, delegate cleanup

chrome/service/cloud_print/print_system.h

Index: chrome/service/cloud_print/print_system.h
diff --git a/chrome/service/cloud_print/print_system.h b/chrome/service/cloud_print/print_system.h
index 3f35cf2defd0b6063a3b894da81640b994868908..a5463b4e6721bffe126dceb6c08ff8a78f4ec30f 100644
--- a/chrome/service/cloud_print/print_system.h
+++ b/chrome/service/cloud_print/print_system.h
@@ -119,10 +119,12 @@ class PrintSystem : public base::RefCountedThreadSafe<PrintSystem> {
    public:
     // Callback interface for JobSpooler notifications.
     class Delegate {
-      public:
-        virtual ~Delegate() { }
-        virtual void OnJobSpoolSucceeded(const PlatformJobId& job_id) = 0;
-        virtual void OnJobSpoolFailed() = 0;
+     public:
+      virtual void OnJobSpoolSucceeded(const PlatformJobId& job_id) = 0;
+      virtual void OnJobSpoolFailed() = 0;
+
+     protected:
+      virtual ~Delegate() {}
     };
 
     // Spool job to the printer asynchronously. Caller will be notified via