It turned out that the original implementation was broken
from the beginning. This patch fixes the API to return
the correct one.

GetIncumbentContext was implemented at
https://chromium-review.googlesource.com/c/v8/v8/+/536728

Change-Id: Iba29171bac10ed82575a8079396768a9d5af3b13
Bug: chromium:883036
Reviewed-on: https://chromium-review.googlesource.com/1219368
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55874}