"obtain a browsing context to use for a navigation response" appears to have easy-to-hit assert

[annevk]

As far as I can tell this algorithm is unconditionally invoked by "create and initialize a Document object" which we use for most Document object creation. Which in turn means that

Assert: browsingContext is a top-level browsing context.

is easily hit. Am I missing something or should that be an early return (or a conditional in calling algorithms)?

cc @camillelamy @hemeryar

[domenic]

Yeah, this seems pretty busted. Probably step 1 should instead be

1. If browsingContext is not a top-level browsing context, return browsingContext.

I hope @camillelamy or @hemeryar can confirm.

[camillelamy]

Ah yes indeed, this seems to be an error. We should do what @domenic suggests. I think there used to be a guard in "create and initialize a Document object" to only call it when COOP required it (which implies a top-level navigation). But since there isn't anymore, we should just return the current browsing context for child browsing contexts.

[hemeryar]

I'm not sure which protection existed in the first place, but I agree that we should simply return the current BrowsingContext for subframes.