Don't try to guess the referrer policy, but use the one associated with the request

This is possible now that we store the referrer policy on each request.

BUG=334125
R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/135973009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248650 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248650