Chrome Version: 55.0.2883.95
OS: macOS 10.12.2

What steps will reproduce the problem?
(1) Open http://w3c-test.org/html/semantics/forms/the-label-element/label-attributes.html in Chrome.
(2) Observe the test results.

What is the expected result?
All the tests on the page should pass.

What happens instead?
One of the tests fails:
Fail
A label element not in a document can not label any element in the document.	
assert_not_equals: A label element not in a document should not label an element in a document. got disallowed value Element node <input id="test1"></input>

Further details:
The test in question basically does:
    var label = document.createElement("label");
    label.htmlFor = "idOfAnInputInTheDocument";
    assertEqual(label.control, null);
And the assertion fails because `.control` returns the corresponding <input> instead of null.

Per https://html.spec.whatwg.org/multipage/#dom-label-control
> The `control` IDL attribute must return the label element's **labeled control**, if any,
> or null if there isn't one.

Per https://html.spec.whatwg.org/multipage/#attr-label-for
> If the [`for`] attribute is specified, the attribute's value must be
> the ID of a labelable element in the same **tree** as the label element.
> If the [`for`] attribute is specified
> and there is an element in the **tree** whose ID is equal to the value of the `for` attribute,
> and the first such element in tree order is a labelable element,
> then that element is the label element's **labeled control**.

And **tree** is defined by https://dom.spec.whatwg.org/#concept-tree
Since `label.parentNode === null` in our case,
my reading is that the <label> and the <input> are in different trees.

Therefore, the <label> has no **labeled control** and HTMLLabelElement.control should return null.