Add markPromiseAsHandled V8 extra util

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 47 matching lines @@
 
     const fulfilledPromise2 = Promise_resolve(call(function (arg1, arg2) {
       return (this.prop === arg1 && arg1 === 'value' && arg2) ? 2 : -1;
     }, { prop: 'value' }, 'value', arraysOK));
 
     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);
+
     return {
       privateSymbol: v8.createPrivateSymbol('sym'),
       fulfilledPromise, // should be fulfilled with 1
       fulfilledPromise2, // should be fulfilled with 2
-      rejectedPromise // should be rejected with 3
+      rejectedPromise, // should be rejected with 3
+      rejectedButHandledPromise // should be rejected but have a handler
     };
   };
 })