commit c1a31b1aeb343867b3f835aa50cccadc4b7569b0
author Caitlin Fischer <caitlinfischer@google.com> Tue Feb 08 19:40:32 2022
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Tue Feb 08 19:40:32 2022
tree 316bc224901d7a58bed1f5c0531753c8fbca29b0
parent 072b6bf1b7db7f8b8cf2e2e3127a98a6b859d7bb

Have Chrome apply client-side defaults when the safe seed is empty.

More specifically, if Variations Safe Mode is triggered (see
SafeSeedManager::ShouldRunInSafeMode()) and the safe seed is empty,
then this change makes Chrome apply client-side defaults (e.g.
DISABLED_BY_DEFAULT).

The status quo behavior has Chrome continue to apply the regular
variations seed when the safe seed should be used but is empty. This is
problematic because a client (a) whose regular seed has an experiment
that renders Chrome unusable and (b) whose safe seed is empty will be
stuck in a bad state. New clients, in particular, have empty safe
seeds.

This change also updates a relevant enum: SeedUsage.

kCorruptedSeedNotUsed (value 2) is renamed kUnloadableRegularSeedNotUsed.
This is a more accurate description since corrupted regular seeds,
regular seeds with invalid signatures, and empty regular seeds were and
still are associated with this enumerator. There are no changes to the
kinds of regular seeds being associated with
kUnloadableRegularSeedNotUsed (né kCorruptedSeedNotUsed).

The following enums are deprecated:
* kCorruptedSafeSeedNotUsed (value 5),
* kRegularSeedUsedAfterEmptySafeSeedLoaded (value 6),
* kExpiredRegularSeedNotUsedAfterEmptySafeSeedLoaded (value 7), and
* kCorruptedRegularSeedNotUsedAfterEmptySafeSeedLoaded (value 8).

The enumerators with values 6 to 8 are no longer applicable since
regular seeds will no longer be applied if Chrome tries to trigger
Variations Safe Mode and encounters an empty safe seed.

kCorruptedSafeSeedNotUsed was associated with safe seeds with invalid
signatures and corrupted safe seeds. It was not associated with empty
safe seeds. Going forward, empty safe seeds, corrupted safe seeds, and
safe seeds with invalid signatures will be treated in the same way: they
will not be applied. Instead of reusing kCorruptedSafeSeedNotUsed, we
replace it with kUnloadedSafeSeedNotUsed as it would be confusing for
kCorruptedSafeSeedNotUsed to be associated with different kinds of safe
seeds before and after M100.

Bug: 1216953
Change-Id: I835cba158c5ea1cc36498699e6b78cfe70d7209b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3438766
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/main@{#968491}