... by making sure we deopt when the buffer is detached.

Bug: chromium:1074736
Change-Id: I86e4e63014767766d7c079c3a3e38d947c76ef10
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2168874
Commit-Queue: Georg Neis <neis@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67437}