Verify that Referer Policy within Content-Disposition:attachment sandbox is always...

Verify that Referer Policy within Content-Disposition:attachment sandbox is always ReferrerPolicyNever
https://bugs.webkit.org/show_bug.cgi?id=152260
<rdar://problem/23884579>

Reviewed by Andy Estes.

* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-expected.txt: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-always-expected.txt: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-always.html: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-default-expected.txt: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-default.html: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-never-expected.txt: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-never.html: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-no-referrer-expected.txt: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-no-referrer-when-downgrade-expected.txt: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-no-referrer-when-downgrade.html: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-no-referrer.html: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-origin-expected.txt: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-origin.html: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-unsafe-url-expected.txt: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped-with-meta-referer-unsafe-url.html: Added.
* http/tests/contentdispositionattachmentsandbox/referer-header-stripped.html: Added.
* http/tests/contentdispositionattachmentsandbox/resources/referer-header-stripped-frame.php: Added.
* http/tests/contentdispositionattachmentsandbox/resources/referer-header-stripped.js: Added.
* http/tests/contentdispositionattachmentsandbox/resources/subresource-request-not-include-referer-header-frame.php: Removed.
* http/tests/contentdispositionattachmentsandbox/subresource-request-not-include-referer-header-expected.txt: Removed.
* http/tests/contentdispositionattachmentsandbox/subresource-request-not-include-referer-header.html: Removed.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@194128 268f45cc-cd09-0410-ab3c-d52691b4dbfc