Remove linked_ptr from sync.

BUG=556939

Change-Id: I5844f49797be8fcf79bf5ff7e848f164ff5ec9a3
Reviewed-on: https://chromium-review.googlesource.com/c/1379267
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#617539}
11 files changed