Also correct a broken link. Not even w3.org URLs are that cool.

Helps with whatwg/meta#174.

It actually takes a string, so calls should be clear about that.

In particular, remove their activation behavior, stop them from matching
:link and :visited, and stop suggesting that they be focusable areas.

This also includes a slight expansion and rearrangement of the link
element's section to make it clearer what hyperlinks created by <link>
are meant for, contrasting them to <a> and <area> hyperlinks.

Closes whatwg#4831. Closes whatwg#2617. Helps with whatwg#5490.

These are no longer needed as of e4330d5.

Use more HTTPS and drop obsolete HTML Differences reference.

We use en-US these days. Spotted in https://twitter.com/iso2022jp/status/1352601086519955456.

See w3c/csswg-drafts#4278.

The new version matches implementation reality and CSSWG resolution.

The algorithm was also inconsistent, as it looked at whether
the element was in a shadow tree or in the document tree, but it was
only specified to be re-run if the element becomes connected or
disconnected.

The CSSWG discussed this in
w3c/csswg-drafts#3096 (comment)
and http://wpt.live/shadow-dom/ShadowRoot-interface.html tests this.

This also matches closer the definition of <link rel="stylesheet">,
which does use connectedness (though it uses "browsing-context
connected", which is a bit different):
https://html.spec.whatwg.org/#link-type-stylesheet

This contains a small bug fix, in that confirm() and prompt() said
"return" in some cases instead of "return false" or "return null" as
appropriate.

Other notable changes, all editorial, are:

* Factoring out repeated "cannot show simple dialogs" steps, which will
  likely expand over time (see e.g. whatwg#6297).
* Separating out and explaining the no-argument overload of alert().
* Passing the document through to the "printing steps", instead of just
  having them talk about "this Window object".

They are only supported by one engine (Gecko).

Closes whatwg#2957.

Fixes whatwg#6328.

Complements whatwg/fetch#1149.

Closes whatwg#5213.

It has been found in whatwg#6306 that this was an oversight at the time of its introduction. Current behavior goes against author expectations and no implementer has opposed the change to "no-clip".

Tests: web-platform-tests/wpt#27040.

Closes whatwg#6306.

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 relevant algorithm from the Content Security Policy spec.

A follow-up to:

* whatwg#5694
* whatwg#5916

Part of whatwg#6003.

Closes whatwg#5407.

@@iterator is implicitly installed by defining an indexed property getter. Since there is no other way to define it exclusively, this restores some methods back to being indexed getters.

This fixes an inadvertent observable behavior change in d4f07b8.

Also, network scheme is now reduced to HTTP(S) scheme.

Helps with whatwg#5375, but form submission issue remains.

See whatwg/fetch#1166 for context.

Nobody but XMLHttpRequest take a dependency on this please. You have been warned.

Context: whatwg/xhr#311.

Fixes whatwg#6374.