filter out .caller from other worlds

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index 50b6a2bd377011ea0e6a96e1446dc2247d1109aa..faaa6ecce1b15a026fae0f9ea47bfa2424593e43 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -439,6 +439,11 @@ 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);