Add markPromiseAsHandled V8 extra util

src/js/promise.js

Index: src/js/promise.js
diff --git a/src/js/promise.js b/src/js/promise.js
index d7e25124708737f8c5031e8d86d0d20b31176be1..0b37c643d10dcaa6bec39cbad845da534165c4d8 100644
--- a/src/js/promise.js
+++ b/src/js/promise.js
@@ -587,6 +587,10 @@ function PromiseHasUserDefinedRejectHandler() {
   return PromiseHasUserDefinedRejectHandlerRecursive(this);
 };
 
+function MarkPromiseAsHandled(promise) {
+  SET_PRIVATE(promise, promiseHasHandlerSymbol, true);
+}
+
 
 function PromiseSpecies() {
   return this;
@@ -632,7 +636,8 @@ utils.InstallFunctions(GlobalPromise.prototype, DONT_ENUM, [
 utils.InstallFunctions(extrasUtils, 0, [
   "createPromise", PromiseCreate,
   "resolvePromise", ResolvePromise,
-  "rejectPromise", DoRejectPromise
+  "rejectPromise", DoRejectPromise,
+  "markPromiseAsHandled", MarkPromiseAsHandled
 ]);
 
 utils.Export(function(to) {