Missing test for async function where @@species is not called

[littledan]

V8 initially used a naive implementation of async/await which just called the original value of Promise.prototype.then to chain things together. However, this is incorrect, as it uses @@species. Maybe we should have a test in test262 that asserts that this is not accessed, as it seems like a likely bug to run into. bug fix @caitp

[littledan]

FWIW we found and fixed more async/await spec compliance issues that test262 didn't test for in https://codereview.chromium.org/2219623002/ .

[ajklein]

Found some more cases that we got wrong, two in particular:

1. await is not allowed in arrow params inside async functions (spec), i.e.,
   async function f() { var g = (await) => {} }
2. await as an IdentifierReference in an object literal (i.e., var e = {await})

(1) is definitely something I think the tests should cover (since there's a specific early error for it in the spec). (2) is more iffy, but I don't see much harm in including a test for it.

[bterlson]

2 is a good test, I say include it.