Today I learned that the way the Google FIDO u2f polyfill is written means the API defined at https://fidoalliance.org/specs/fido-u2f-v1.0-nfc-bt-amendment-20150514/fido-u2f-javascript-api.html#high-level-javascript-api … can't actually be shipped in non-Chrome browsers in that form because the polyfill will stomp on it with code that only works in Chrome.
Well, I need a callable that does IDL-defined argument processing... Since that tweet, I have switched to just a Function and changes to our code generator to allow me to create that Function sanely from the relevant getter, because I realized people might bind() these things.