Prerender: Check `focus()` Can Make Elements Active

Bug: 1186604
Change-Id: I33e070a1e3797d8a46324c883fe7d28730c46648
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2772681


Reviewed-by: Adithya Srinivasan <adithyas@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Lingqi Chi <lingqi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#864691}