The other option here is to remove aria-owns altogether and revert bug 1535659. That effectively gets us back to the behaviour before bug 1513337 (since aria-owns was a no-op before then). That's a bit ugly (and results in an extra announcement of "combo box" in NVDA at least when the suggestions list gets focus), but probably less work.
Bug 1567377 Comment 1 Edit History
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The other option here is to remove aria-owns altogether and revert bug 1535659. That effectively gets us back to the behaviour before bug 1513337 (since aria-owns was a no-op before then). That's a bit ugly (and results in an extra announcement of "combo box" in NVDA at least when the suggestions list gets focus), but probably less work (and lower risk).