Remove references to CSP plugin-types

[antosart]

With Flash not being supported anymore, the CSP directive plugin-types
has lost its main reason for being and is being removed from the
Content Security Policy specification:
w3c/webappsec-csp#456

This change removes references to the relative algorithm in the
Content Security Policy spec.

• At least two implementers are interested (and none opposed):
  • Chrome
  • Firefox (since they never implemented plugin-types)
• Tests are written and can be reviewed and commented upon at:
  • Remove references to CSP plugin-types #6292
• Implementation bugs are filed:
  • Chrome: https://bugs.chromium.org/p/chromium/issues/detail?id=1168001
  • Firefox: N/A
  • Safari: https://bugs.webkit.org/show_bug.cgi?id=220724

(See WHATWG Working Mode: Changes for more details.)

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/acknowledgements.html ( diff )
/iframe-embed-object.html ( diff )
/infrastructure.html ( diff )

[domenic]

Always excited about some cleanup!

I have a question about PDFs, which I left in w3c/webappsec-csp#456 (comment) , which we should resolve before merging this.

[domenic]

Can you restore the pull request template that was deleted, so that we can fill out the checkboxes (implementer interest, tests, bugs filed) appropriately?

[antosart]

Ok, it took me some time because of other stuff to do in between, but I opened a PR for the test: web-platform-tests/wpt#27499

[domenic]

Perfect, thanks! I updated the original post to indicate this has Mozilla support (since they never shipped plugin-types), so all the boxes are checked and we can merge this now.

[annevk]

I think pr-preview overwrote your changes, but yeah, agreed.