GitLab

We don't run ash_unittests with --enable-features=Mash anymore, so
manually turn on the flag to test the feature.

Bug: 840391
Test: ash_unittests
Change-Id: Idb61128d9a65cbc6e93095683247c3e8cd714a9d
Reviewed-on: https://chromium-review.googlesource.com/1134418Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574405}