Fix unused variable warning in serialize.cc

src/serialize.cc

Index: src/serialize.cc
===================================================================
--- src/serialize.cc	(revision 2973)
+++ src/serialize.cc	(working copy)
@@ -1632,8 +1632,7 @@
   obj->IterateBody(type, size, this);
 
   if (type == CODE_TYPE) {
-    Code* code = Code::cast(obj);
-    LOG(CodeMoveEvent(a, code->address()));
+    LOG(CodeMoveEvent(a, obj->address()));
   }
   objects_++;
   return o;