Safety check on Android: added the last run timestamp to the UI

UI demo: https://screenshot.googleplex.com/PdYajrS8FfE.gif

Bug: 1070620, 1107807
Change-Id: I2fac517d4aefd5999449988cfe7d289f76e67563
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2303714


Reviewed-by: Theresa <twellington@chromium.org>
Reviewed-by: Natalie Chouinard <chouinard@chromium.org>
Reviewed-by: Martin Šrámek <msramek@chromium.org>
Commit-Queue: Andrey Zaytsev <andzaytsev@google.com>
Auto-Submit: Andrey Zaytsev <andzaytsev@google.com>
Cr-Commit-Position: refs/heads/master@{#791461}