The new version supports '$ParanoidMode CheckPresence' in ensure files.

R=iannucci@chromium.org
BUG=794764

Change-Id: I8add0ebbaa324fedf99959a0a5d1301172ef3704
Reviewed-on: https://chromium-review.googlesource.com/1138732
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>