Add back support for "none" referrer policy

It's a legacy keyword that was accidentially removed

BUG=615608
R=estark@chromium.org

Change-Id: I1bf4d87d999f35b30beca644b4dec6712ac2d388
Reviewed-on: https://chromium-review.googlesource.com/772234
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517114}
2 files changed