This adds support for macOS 10.13 "High Sierra"

BUG=chromium:774309

Change-Id: I9b5b13750608f703dd0a3e0afeb1e314b437b8cc
Reviewed-on: https://chromium-review.googlesource.com/721520
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>