This proposal has not moved beyoned stage 2 in two years, and has never
moved past the HARMONY_INPROGRESS state in flag-definitions.h.

It was originally added to aide in desugaring yield*, but is no longer
used for that purpose.

Bug: v8:4700, v8:7310
Change-Id: Ieca40d8e4bf565516bbe71e47b996daa70d2e835
Reviewed-on: https://chromium-review.googlesource.com/935297
Commit-Queue: Adam Klein <adamk@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51582}