[streams] Fix ReadableStream constructor if not getting a promise as startResult (#250)

In the examples we have cases where the result of invoking the start
is undefined and we treat it as something acceptable, therefore the
constructor should be prepared to operate in that case.

I guess this should also apply to other cases, like the WritableStream constructor, cancel functions, etc.
You can merge this Pull Request by running:

  git pull https://github.com/calvaris/streams constructor

Or you can view, comment on it, or merge it online at:

  https://github.com/whatwg/streams/pull/250

-- Commit Summary --

  * Fix ReadableStream constructor if not getting a promise as startResult

-- File Changes --

    M index.bs (1)

-- Patch Links --

https://github.com/whatwg/streams/pull/250.patch
https://github.com/whatwg/streams/pull/250.diff

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/streams/pull/250