"top-level browsing context" reference incorrect/outdated

[domenic]

If the relevant global object of this is not a top-level browsing context

First, the global object will be a Window. You cannot use the predicate "top-level browsing context" on a Window object; they're different things.

Second, in whatwg/html#6315 we generally moved away from browsing contexts.

So, the right way to do this is:

If [=this=]'s [=relevant global object=]'s [=Window/navigable=] is not a [=top-level traversable=], then...