GitLab

- Return nullptr key when local sync is enabled and avoid DCHECK

Bug: 1023827
Change-Id: I73fac96233ff0b17611b8d0ffb150d9977417d50
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1911218
Commit-Queue: Alex Chau <alexchau@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714630}