8008796: SA: Oop.iterateFields() should support CompressedKlassPointers again

Summary: add a missing change from JDK-7054512 so that Oop.iterateFields() works with UseCompressedKlassPointers
Reviewed-by: coleenp, roland
Contributed-by: yunda.mly@taobao.com

agent/src/share/classes/sun/jvm/hotspot/oops/Oop.java

 /*
- * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 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
@@ -148,7 +148,7 @@ public class Oop {
     if (doVMFields) {
       visitor.doCInt(mark, true);
       if (VM.getVM().isCompressedKlassPointersEnabled()) {
-        throw new InternalError("unimplemented");
+        visitor.doMetadata(compressedKlass, true);
       } else {
         visitor.doMetadata(klass, true);
       }