arc: M58: Set migration success notification pref.
The code for M59 or above expects the flag to be already set
if the user started using the new filesystem from the very
beginning they started using the device. M58 needs to set it.
Cherry-pick from the following four changes
1. crrev.com/2788383003 (Only pref name addition)
2. crrev.com/2813633002 (Only BUILD.gn addition)
3. crrev.com/2808353008 (UpdateArcFileSystemCompatibilityPrefIfNeeded)
4. crrev.com/2828213002 (ShowArcMigrationSuccessNotificationIfNeeded)
with unneeded part (disabling ARC or showing notification based on the flag) removed.
BUG=716976
TEST=Manually checked the pref value is set to 2 on M58 Reef.
R=hidehiko@chromium.org
Review-Url: https://codereview.chromium.org/2850123002 .
Cr-Commit-Position: refs/branch-heads/3029@{#788}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
8 files changed
