Async generators didn't correctly handle the situation where one calls
.return on a suspended-at-start async generator and passes a
promise-like object whose awaiting causes a new request to the
generator.

Bug: chromium:805729
Change-Id: I4da13ab5bd97f8c2a2c5373242a2d5e2ab0f7f10
Reviewed-on: https://chromium-review.googlesource.com/891231Reviewed-by: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50974}

BUG=chromium:797581

Change-Id: I08f880a907f122480a014763975ecc07e2c49f7d
Reviewed-on: https://chromium-review.googlesource.com/856937Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50471}

The checked node and used node were mismatched. It checked if
"var_unique" is a string, but it used "key" which may not be a string.

Bug: v8:4911, v8:7161, chromium:800077
Change-Id: Ia2aee8b77ac33500430365a4800bf9cca40a28fc
Reviewed-on: https://chromium-review.googlesource.com/855138Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50435}