[Android][SafeMode] Use safe values

When Safe Mode for Cached Flags is engaged and the feature flag is
enabled, use safe values if they are present. If not present or
written by a different version, use default values instead.

Bug: 1199069
Change-Id: I7cc0680a56c304ba1154744bfbdbc5b6fad1b60f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3645585


Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Roger McFarlane <rogerm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1029929}