Aaron Wells authored Feb 04, 2016 and Robert Lyon committed Mar 22, 2016

X-XSS-Protection: Tells the browser not to disable XSS protection

X-Content-Type-Options: Tells the browser not to try to guess at
mimetypes of downloads

X-Permitted-Cross-Domain-Policies: Tells Flash & PDF not to trust
alternate crossdomain.xml files (which set the permissions on whether
this site allows itself to be accessed by scripts in Flash & PDF).
Prevents an attacker from uploading a more permissive crossdomain.xml

X-Powered-By: PHP by default sends this header with the current full
PHP version.

behatnotneeded: Selenium can't examine HTTP response headers

Change-Id: Ia2a6de971fc62b7d8806ad010aa0fbe37c1a7357
(cherry picked from commit 29656f03)