They will later be detected as redundant again, but we can save memory
and performance by just not adding them in the first place.

R=mvstanton@chromium.org

Bug: v8:8423
Change-Id: I11d88642333681612e2f8f4eaee7ba700cbf64d5
Reviewed-on: https://chromium-review.googlesource.com/c/1390132Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58479}