GitLab

This allows to expose certain methods only on the impl,
not on the public interface.

Bug: chromium:1069378
Change-Id: I3623aadb5f9d9ebb7f2dae4c78cb830ee74f55b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2426043Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809752}