Add a Mac 10.12 tests target.

BUG=707909

Review-Url: https://codereview.chromium.org/2843503004
Cr-Original-Commit-Position: refs/heads/master@{#466777}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 858c1cc4ded16a2365425fa416bb90d3c2d3bf85
1 file changed