Update class layout for j.l.ref.Reference.

One additional vtable entry.

Change-Id: I34c951739def06a9e27c0b44f8a7e83613541537
diff --git a/runtime/mirror/reference-inl.h b/runtime/mirror/reference-inl.h
index b353402..3c348ff 100644
--- a/runtime/mirror/reference-inl.h
+++ b/runtime/mirror/reference-inl.h
@@ -23,7 +23,7 @@
 namespace mirror {
 
 inline uint32_t Reference::ClassSize() {
-  uint32_t vtable_entries = Object::kVTableLength + 5;
+  uint32_t vtable_entries = Object::kVTableLength + 4;
   return Class::ComputeClassSize(false, vtable_entries, 2, 0, 0);
 }