Measure resources from private IP addresses in public websites.

This patch gathers data in the hopes of measuring the impact of locking
down private-IP-address subresources in public-IP-address sites. It does
so after the response has been delivered, so it's not the way we'd want
to do checking if we wanted to block the request, but it's a good way of
getting numbers so we can make decisions.

BUG=378566

Review URL: https://codereview.chromium.org/564123002

git-svn-id: svn://svn.chromium.org/blink/trunk@182053 bbb929c8-8fbe-4397-9dbb-9b2b20218538