Feature policy container policies may be different depending on the type of frame owner. Current code doesn't care, and constructs container policies identically regardless of frame owner type.
-- Within <frame> tags, fullscreen needs to be disabled regardless of declared policy. (See spec at https://fullscreen.spec.whatwg.org/#model)
-- Iframes support additional attributes which other frame owner elements do not.
Comment 1 by lunalu@chromium.org
, Jun 12 2017