https://github.com/tc39/ecma262/pull/1776 is a normative change that
reached consensus in the November 2019 TC39. It changes
%AsyncFromSyncIteratorPrototype% methods to forward the absence of
arguments to the underlying sync iterator. This is observable via
`arguments.length` inside the underlying sync iterator.

For example, .next is changed to, roughly:

```
%AsyncFromSyncIteratorPrototype%.next = function(value) {
  let res;
  if (arguments.length < 1) {
     res = [[SyncIteratorRecord]].[[Iterator]].next();
  } else {
     res = [[SyncIteratorRecord]].[[Iterator]].next(value);
  }
  // ...
};
```

Bug: v8:10395
Change-Id: Ib8127d08cd78b8d502e6510241f3f13fbbaba5c7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247041Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68398}