net: implement the beginnings of HSTS pinning

(Based on a patch by Chris Evans.)

Doesn't yet actually get the information from the HSTS header, but all the
infrastructure is in place.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/6835033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@81584 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed