Add V8 extra utils for promise state

test/cctest/test-extra.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function (global, binding, v8) {
   'use strict';
   binding.testExtraShouldReturnFive = function() {
     return 5;
   };
 
@@ skipping 52 matching lines @@
 
     const rejectedPromise = v8.createPromise();
     v8.rejectPromise(rejectedPromise, apply(function (arg1, arg2) {
       return (arg1 === arg2 && arg2 === 'x') ? 3 : -1;
     }, null, new v8.InternalPackedArray('x', 'x')));
 
     const rejectedButHandledPromise = v8.createPromise();
     v8.rejectPromise(rejectedButHandledPromise, 4);
     v8.markPromiseAsHandled(rejectedButHandledPromise);
 
+    function promiseStateToString(promise) {
+      switch (v8.promiseState(promise)) {
+        case v8.kPROMISE_PENDING:
+          return "pending";
+        case v8.kPROMISE_FULFILLED:
+          return "fulfilled";
+        case v8.kPROMISE_REJECTED:
+          return "rejected";
+        default:
+          throw new Error("Unexpected value for promiseState");
+      }
+    }
+
+    let promiseStates = promiseStateToString(new Promise(() => {})) + ' ' +
+                        promiseStateToString(fulfilledPromise) + ' ' +
+                        promiseStateToString(rejectedPromise);
+
     return {
       privateSymbol: v8.createPrivateSymbol('sym'),
       fulfilledPromise, // should be fulfilled with 1
       fulfilledPromise2, // should be fulfilled with 2
       rejectedPromise, // should be rejected with 3
-      rejectedButHandledPromise // should be rejected but have a handler
+      rejectedButHandledPromise, // should be rejected but have a handler
+      promiseStates // should be the string "pending fulfilled rejected"
     };
   };
 })