There was a helpful TODO telling where it should live.

BUG=v8:5402,v8:6921

Change-Id: Id9022c72c9e7de8d76ea0db964217b766299195d
Reviewed-on: https://chromium-review.googlesource.com/718337Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48524}