[streams] Should ReadableStreamController be visible? (#322)

>From my reading of the spec, it seems that ReadableStream, ReadableStreamReader and ReadableStreamController should all be visible from ECMAScript.
It makes sense for ReadableStream.
It makes somehow sense for ReadableStreamReader.
It does not seem necessary for ReadableStreamController.
Is there a need for that?

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/streams/issues/322