I will take this bug, but I would narrow down the bug to fix top level principal in permision delegation, by moving the getPermission to parent. Another part of the moving is in patch
Bug 1587743 Comment 9 Edit History
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I will take this bug, but I would narrow down the bug to fix top level principal in permision delegation, by moving the getPermission to parent. Another moving of getting top principal to parent is in patch https://phabricator.services.mozilla.com/D53261