In http://dev.w3.org/2006/webapi/WebIDL/#idl-dictionaries there's this text:
A dictionary MUST NOT be declared such that its inheritance hierarchy has a
cycle. That is, an interface A cannot inherit from itself, nor can it inherit
from another interface B that inherits from A, and so on.
That needs some s/interface/dictionary/
Thanks, fixed, and also in the Exceptions section.