Check that Promise subclasses have callable resolve/reject

src/messages.h

Index: src/messages.h
diff --git a/src/messages.h b/src/messages.h
index 8f5684f41658e762c4d937211279e887f3d58240..35e7c7f85cd9b2d2dc1ea06c913447613e2d8cce 100644
--- a/src/messages.h
+++ b/src/messages.h
@@ -187,6 +187,7 @@ class CallSite {
   T(PromiseCyclic, "Chaining cycle detected for promise %")                    \
   T(PromiseExecutorAlreadyInvoked,                                             \
     "Promise executor has already been invoked with non-undefined arguments")  \
+  T(PromiseNonCallable, "Promise resolve or reject function is not callable")  \
   T(PropertyDescObject, "Property description must be an object: %")           \
   T(PropertyNotFunction,                                                       \
     "'%' returned for property '%' of object '%' is not a function")           \