Similar to marking, seed the pointers updating with items.

Bug: chromium:726040
Change-Id: Iaa480d153de96d744c425c478c68e7629550c85a
Reviewed-on: https://chromium-review.googlesource.com/521145Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45666}