Reland "mark platform un-availability""

This reverts commit 6e1fa445.

Reason for revert: relanding a reverted changed

Bug: 153073816
Test: m

Exempt-From-Owner-Approval: cherry-pick from AOSP

Merged-In: I3735866776cf6eb0320c9fb8c6be8ac0c48baa1c
(cherry picked from commit 403c255b)
Change-Id: I3735866776cf6eb0320c9fb8c6be8ac0c48baa1c