Html: Minimize the usage of the incumbent concept

[domenic]

This is a tracking bug, both for HTML and for the wider web ecosystem, to see if we can minimize the number of places that use the incumbent global/settings object/realm. Originally this was https://www.w3.org/Bugs/Public/show_bug.cgi?id=26603.

Here is our HTML checklist:

• [x] [Same-origin check for contentDocument](https://html.spec.whatwg.org/#nested-browsing-contexts:incumbent-settings-object) [#1541]
• [ ] [window.close()](https://html.spec.whatwg.org/#apis-for-creating-and-navigating-browsing-contexts-by-name:concept-incumbent-global)
• [x] [data: URL document origins](https://html.spec.whatwg.org/#origin:incumbent-settings-object)
• [ ] [non-initial about:blank URL document origins](https://html.spec.whatwg.org/#navigate) (see _incumbentNavigationOrigin_
• [ ] [Location-object navigate](https://html.spec.whatwg.org/#the-location-interface:incumbent-settings-object) (@bholley says this one probably has to stick around)
• [x] [alert()/confirm()/prompt() sandboxing](https://html.spec.whatwg.org/#simple-dialogs:incumbent-settings-object) [#1473]
• [x] [print() sandboxing](https://html.spec.whatwg.org/#printing:incumbent-settings-object) [#1473]
• [ ] [postMessage's origin check of "/" and resulting MessageEvent](https://html.spec.whatwg.org/#posting-messages:incumbent-settings-object) [#1542, #1573] (per #1542 this should stay incumbent, at least unless we get rid of every other incumbent usage)
• [x] [MessageChannel's ports' owner](https://html.spec.whatwg.org/#message-channels:incumbent-settings-object) [#5728]
• [x] [BroadcastChannel's owner](https://html.spec.whatwg.org/#broadcasting-to-other-browsing-contexts:incumbent-settings-object) [#5729]
• [x] [Setting up a worker](https://html.spec.whatwg.org/#dedicated-workers-and-the-worker-interface:incumbent-settings-object) (see also SharedWorker) [#1472]
• [x] [importScripts](https://html.spec.whatwg.org/#importing-scripts-and-libraries:incumbent-settings-object) [#1963]

Other specs:

• [x] Credential Management https://github.com/w3c/webappsec-credential-management/issues/53
• [x] Blob URLs https://github.com/w3c/FileAPI/issues/60
• [ ] cssom-view https://github.com/w3c/csswg-drafts/issues/1725
• [x] Sensor API https://github.com/w3c/sensors/issues/253
• [ ] Battery Status API https://github.com/w3c/battery/issues/19

If you have other specs that use the incumbent concept, comment here and I will update the OP.

[xfq]

I just filed w3c/csswg-drafts#1725 and w3c/sensors#253.

[anssiko]

@domenic, w3c/sensors [updated], so you can tick that box in the OP.

[littledan]

Thanks for this great documentation, @domenic . I missed the big warning in the HTML spec when trying to edit the WebNFC spec; thanks for pointing out the error.

What if we renamed the incumbent to "legacy incumbent" (and ditto for "legacy entry")? The use of this sort of wording in WebIDL makes everything really clear.

[domenic]

That's probably a good idea, thanks for the suggestion! A PR would be appreciated.