filter out .caller from other worlds

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index 978e58282d2fd94660f422fee43c3bf6a22cfaf4..fd60a89ad7ed6412e25e497c6aaa22c3cb65844d 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -449,6 +449,11 @@ class Context: public FixedArray {
     return map == map->GetHeap()->global_context_map();
   }
 
+  bool HasSameSecurityTokenAs(Context* that) {
+    return this->global_object()->native_context()->security_token() ==
+        that->global_object()->native_context()->security_token();
+  }
+
   // A native context holds a list of all functions with optimized code.
   void AddOptimizedFunction(JSFunction* function);
   void RemoveOptimizedFunction(JSFunction* function);