Desugar async/await to create the resulting Promise upfront

src/js/promise.js

 // Copyright 2012 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, utils, extrasUtils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 363 matching lines @@
     // equivalent to throwing an exception directly.
     %PromiseRejectEventFromStack(promise, r);
     return promise;
   } else {
     var promiseCapability = NewPromiseCapability(this, true);
     %_Call(promiseCapability.reject, UNDEFINED, r);
     return promiseCapability.promise;
   }
 }
 
-// Shortcut Promise.reject and Promise.resolve() implementations, used by
-// Async Functions implementation.
-function PromiseCreateRejected(r) {
-  var promise = PromiseCreateAndSet(kRejected, r);
-  // This is called from the desugaring of async/await; no reason to
-  // create a redundant reject event.
-  %PromiseRejectEvent(promise, r, false);
-  return promise;
-}
-
-function PromiseCreateResolved(value) {
-  var promise = PromiseInit(new GlobalPromise(promiseRawSymbol));
-  var resolveResult = ResolvePromise(promise, value);
-  return promise;
-}
-
 function PromiseCastResolved(value) {
   if (IsPromise(value)) {
     return value;
   } else {
     var promise = PromiseInit(new GlobalPromise(promiseRawSymbol));
     var resolveResult = ResolvePromise(promise, value);
     return promise;
   }
 }
 
@@ skipping 210 matching lines @@
   "catch", PromiseCatch
 ]);
 
 %InstallToContext([
   "promise_catch", PromiseCatch,
   "promise_create", PromiseCreate,
   "promise_has_user_defined_reject_handler", PromiseHasUserDefinedRejectHandler,
   "promise_reject", DoRejectPromise,
   "promise_resolve", ResolvePromise,
   "promise_then", PromiseThen,
-  "promise_create_rejected", PromiseCreateRejected,
-  "promise_create_resolved", PromiseCreateResolved
 ]);
 
 // This allows extras to create promises quickly without building extra
 // resolve/reject closures, and allows them to later resolve and reject any
 // promise without having to hold on to those closures forever.
 utils.InstallFunctions(extrasUtils, 0, [
   "createPromise", PromiseCreate,
   "resolvePromise", ResolvePromise,
   "rejectPromise", DoRejectPromise
 ]);
 
 utils.Export(function(to) {
   to.PromiseCastResolved = PromiseCastResolved;
   to.PromiseThen = PromiseThen;
 
   to.GlobalPromise = GlobalPromise;
   to.NewPromiseCapability = NewPromiseCapability;
   to.PerformPromiseThen = PerformPromiseThen;
+  to.RejectPromise = RejectPromise;
 });
 
 })