HTMLDocument interface is missing

[Joris-van-der-Wel]

For historical reasons, Window objects must also have a writable, configurable, non-enumerable property named HTMLDocument whose value is the Document interface object.

(line 78382 616df18)

This is not the case in Firefox 53, Chrome 57, Safari 10, IE11:

>> Document === HTMLDocument
false

>> Object.getPrototypeOf(HTMLDocument.prototype) === Document.prototype
true

>> Object.prototype.toString.call(document)
"[object HTMLDocument]"

>> Object.keys(HTMLDocument.prototype).length > 0
true

Nor can I find a HTMLDocument interface in the DOM or HTML spec. This was changed in 83f13ee.

Since all the browsers do not follow the specification, I think the specification should be updated?
(Also, I suspect that scripts in the wild might use the string tag [object HTMLDocument] to detect document objects)

[Joris-van-der-Wel]

Since all the browsers do something different

I meant "Since all the browsers do not follow the specification"

[annevk]

This is whatwg/dom#221 basically. To address it we must first redo how we allocate document objects. That will make it easier to allocate a different one for XML vs HTML, etc. #2657 has some thoughts on how to get there and my three most recent PRs will help us get there I think.

[annevk]

(I need to write more PRs after that, but I'd rather do it in incremental steps since having too many PRs depend on each other gets confusing fast.)

[domenic]

Let's consolidate this into whatwg/dom#221 and #2657.