[es6] Initial steps towards a correct implementation of IsCallable.

src/api-natives.cc

Index: src/api-natives.cc
diff --git a/src/api-natives.cc b/src/api-natives.cc
index 5993859710a5e1d4063b6900c5af6d1168e82a97..48c1a87255e19829a3197643ada3be0baabb08bc 100644
--- a/src/api-natives.cc
+++ b/src/api-natives.cc
@@ -491,9 +491,9 @@ Handle<JSFunction> ApiNatives::CreateApiFunction(
     map->set_has_indexed_interceptor();
   }
 
-  // Set instance call-as-function information in the map.
+  // Mark instance as callable in the map.
   if (!obj->instance_call_handler()->IsUndefined()) {
-    map->set_has_instance_call_handler();
+    map->set_is_callable();
   }
 
   // Recursively copy parent instance templates' accessors,