[whatwg] Workers feedback

[Aaron Boodman]

Ian,

Thanks for taking the time to read and understand all the feedback.

Although this is not my most preferred design for the API, I can live
with it. I'm happy that we removed startConversation(). I think that
was just extra complexity on top of an already large API.

As for putting forward contradictory suggestions, I apologize for
that. In the future, I will try to form final opinions before opining.

Thanks,

- a