(In reply to Dão Gottwald [::dao] from comment #0)
I was wondering if role="combobox" should move to a parent, but wasn't sure because the div doesn't seem to serve any other function in the w3c example and it's unclear what it's good for. I'm now guessing it's needed because otherwise role="combobox" overrides the input's default implied role.
Right, the ARIA role always takes precedence, even on native HTML elements that are widgets. So we have to be careful. Like I said, since I wasn't sure myself, we might need to iterate until we get this right.
There is currently also still another problem that is possibly for a different bug, and that is that the list opens and gains focus the moment I type something in. In the old URL bar, I have to explicitly press DownArrow for the first element to have its activedescendant set, otherwise I could not use the left and right arrow keys to read what I typed. But that might be for a different bug. This is one of the things Jamie Teh finally did right last year when he also introduced the URLbar tests.