[async-await] Move remaining async-await code to TF

src/js/async-await.js

-// Copyright 2016 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();
-
-// -------------------------------------------------------------------
-// Imports
-
-var AsyncFunctionNext;
-var AsyncFunctionThrow;
-
-utils.Import(function(from) {
-  AsyncFunctionNext = from.AsyncFunctionNext;
-  AsyncFunctionThrow = from.AsyncFunctionThrow;
-});
-
-var promiseHandledBySymbol =
-    utils.ImportNow("promise_handled_by_symbol");
-var promiseForwardingHandlerSymbol =
-    utils.ImportNow("promise_forwarding_handler_symbol");
-
-// -------------------------------------------------------------------
-
-function PromiseCastResolved(value) {
-  // TODO(caitp): This is non spec compliant. See v8:5694.
-  if (%is_promise(value)) {
-    return value;
-  } else {
-    var promise = %promise_internal_constructor(UNDEFINED);
-    %promise_resolve(promise, value);
-    return promise;
-  }
-}
-
-// ES#abstract-ops-async-function-await
-// AsyncFunctionAwait ( value )
-// Shared logic for the core of await. The parser desugars
-//   await awaited
-// into
-//   yield AsyncFunctionAwait{Caught,Uncaught}(.generator, awaited, .promise)
-// The 'awaited' parameter is the value; the generator stands in
-// for the asyncContext, and .promise is the larger promise under
-// construction by the enclosing async function.
-function AsyncFunctionAwait(generator, awaited, outerPromise) {
-  // Promise.resolve(awaited).then(
-  //     value => AsyncFunctionNext(value),
-  //     error => AsyncFunctionThrow(error)
-  // );
-  var promise = PromiseCastResolved(awaited);
-
-  var onFulfilled = sentValue => {
-    %_Call(AsyncFunctionNext, generator, sentValue);
-    // The resulting Promise is a throwaway, so it doesn't matter what it
-    // resolves to. What is important is that we don't end up keeping the
-    // whole chain of intermediate Promises alive by returning the value
-    // of AsyncFunctionNext, as that would create a memory leak.
-    return;
-  };
-  var onRejected = sentError => {
-    %_Call(AsyncFunctionThrow, generator, sentError);
-    // Similarly, returning the huge Promise here would cause a long
-    // resolution chain to find what the exception to throw is, and
-    // create a similar memory leak, and it does not matter what
-    // sort of rejection this intermediate Promise becomes.
-    return;
-  }
-
-  var throwawayPromise = %promise_internal_constructor(promise);
-
-  // The Promise will be thrown away and not handled, but it shouldn't trigger
-  // unhandled reject events as its work is done
-  %PromiseMarkAsHandled(throwawayPromise);
-
-  if (DEBUG_IS_ACTIVE) {
-    if (%is_promise(awaited)) {
-      // Mark the reject handler callback to be a forwarding edge, rather
-      // than a meaningful catch handler
-      SET_PRIVATE(onRejected, promiseForwardingHandlerSymbol, true);
-    }
-
-    // Mark the dependency to outerPromise in case the throwaway Promise is
-    // found on the Promise stack
-    SET_PRIVATE(throwawayPromise, promiseHandledBySymbol, outerPromise);
-  }
-
-  %perform_promise_then(promise, onFulfilled, onRejected, throwawayPromise);
-}
-
-// Called by the parser from the desugaring of 'await' when catch
-// prediction indicates no locally surrounding catch block
-function AsyncFunctionAwaitUncaught(generator, awaited, outerPromise) {
-  AsyncFunctionAwait(generator, awaited, outerPromise);
-}
-
-// Called by the parser from the desugaring of 'await' when catch
-// prediction indicates that there is a locally surrounding catch block
-function AsyncFunctionAwaitCaught(generator, awaited, outerPromise) {
-  if (DEBUG_IS_ACTIVE && %is_promise(awaited)) {
-    %PromiseMarkHandledHint(awaited);
-  }
-  AsyncFunctionAwait(generator, awaited, outerPromise);
-}
-
-%InstallToContext([
-  "async_function_await_caught", AsyncFunctionAwaitCaught,
-  "async_function_await_uncaught", AsyncFunctionAwaitUncaught,
-]);
-
-})