Summary:
Apparently during the review of D69265, and my flailing around with
git, a somewhat important line disappeared.
On top of that, there was no test exercising that code path, and
while writing the follow up patch I intended to write, some `CHECK`s
were failing.
Re-add the missing line, and add a test that fails without said line.
Reviewers: hctim, morehouse, pcc, cferris
Reviewed By: hctim
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D69529