This is more idiomatic than using a Promise.

Change-Id: I61443e90ef1c0c589284851ea9be410153919eb5
Reviewed-on: https://chromium-review.googlesource.com/c/456278Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58828}