IIUC, this change means that program with bug that is substituting wrong value to binaryType will be no longer warned by an exception.
Is there any benefit of enum making this change worth?
Wrong values throw TypeError per WebIDL.
Yes for function. Is it true for assignment too?
Example here says it's ignored.
That non-normative example seems wrong. http://dev.w3.org/2006/webapi/WebIDL/#es-enumeration says to throw.
But <http://dev.w3.org/2006/webapi/WebIDL/#es-attributes> has a special case.
The reason to do this is to be consistent with the other enumerated attributes in the platform.
Yeah, the plan here is to be consistent with other things in the platform.
(Good browsers can give a warning in their consoles, btw.)