[Autofill] Remove expired strikes on StrikeDB init

Added GetExpiryTime() to StrikeDatabase interface and removes
expired striked on StrikeDB init.

Bug: 884817
Change-Id: Ie99173b631f668f3be848f1afa925d7feec801ef
Reviewed-on: https://chromium-review.googlesource.com/c/1351887
Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Reviewed-by: Jared Saul <jsaul@google.com>
Commit-Queue: Anne Lim <annelim@google.com>
Cr-Commit-Position: refs/heads/master@{#612754}
6 files changed