Add a context argument to the visitor callback.

Change-Id: I1e49d66043ebe8cbc9cbf5edf167c37bc52fad48
diff --git a/vm/alloc/Visit.h b/vm/alloc/Visit.h
index 5bc9b60..343d567 100644
--- a/vm/alloc/Visit.h
+++ b/vm/alloc/Visit.h
@@ -19,8 +19,8 @@
 
 #include "Dalvik.h"
 
-typedef void Visitor(void *obj);
+typedef void Visitor(void *obj, void *arg);
 
-void dvmVisitObject(Visitor *visitor, Object *obj);
+void dvmVisitObject(Visitor *visitor, Object *obj, void *arg);
 
 #endif /* _DALVIK_ALLOC_VISIT */