Reland "Implement auto command in the update_wpr script"

This is a reland of 68ef44281aace4fa7c5155fcbbd73ea8acd5b305

Original change's description:
> Implement auto command in the update_wpr script
>
> R=perezju@chromium.org
>
> Bug: 895891
> Change-Id: Ib4b6b0ea123b64d0333cb0911930358dcb3ff2ad
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1496871
> Commit-Queue: Sergiy Belozorov <sergiyb@chromium.org>
> Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#637677}

Bug: 895891, 938487
Change-Id: I4dbf7e1adee233598a78772024d71dfebc23e562
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1504014
Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Commit-Queue: Sergiy Belozorov <sergiyb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638049}
4 files changed