CSP: Allow ':80' to match ':443' in source expressions.

https://github.com/w3c/webappsec-csp/commit/22d08b990290e49f5a666fad08de16d75bb369e7#diff-117d6498d2aa8019cc0abf5eeb87a9fa
updated CSP to allow insecure ports to match secure ports in source
expressions. This is a refinement of the change that landed in
https://codereview.chromium.org/1455973003 to address Sniffly.

BUG=625945
R=jochen@chromium.org

Review-Url: https://codereview.chromium.org/2125873003
Cr-Commit-Position: refs/heads/master@{#404127}