6444286: Possible naked oop related to biased locking revocation safepoint in jni_exit()

Summary: Add missing Handle.
Reviewed-by: acorn, dholmes, dice, sspitsyn
Contributed-by: karen.kinnear@oracle.com

src/share/vm/runtime/synchronizer.cpp

 /*
- * Copyright (c) 1998, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -333,7 +333,9 @@ bool ObjectSynchronizer::jni_try_enter(Handle obj, Thread* THREAD) {
 void ObjectSynchronizer::jni_exit(oop obj, Thread* THREAD) {
   TEVENT (jni_exit) ;
   if (UseBiasedLocking) {
-    BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+    Handle h_obj(THREAD, obj);
+    BiasedLocking::revoke_and_rebias(h_obj, false, THREAD);
+    obj = h_obj();
   }
   assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");