GitLab

This class keeps a callback that's called only when it's destructed so
it can only ever be called once. Hence, it should be a OnceClosure.

Bug: 1152268
Change-Id: I39188310b5b2f61547b983ca1d20ab9c1581b505
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2601068Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839755}