[Streams API] Add load-using-streams functionality to XHR or only to Fetch API?

We're implementing Streams API [1] and integration of it and XHR [2]
experimentally in Blink [3][4].

Anne suggested that we look into adding new fetch-layer features to the
Fetch API [5][6] rather than XHR in Blink mailing list (blink-dev) [6].
There's a concern if we can ship the Fetch API to non-ServiceWorker scope
soon [7].

I'd like to hear your opinions on these issues:
- add the feature only to the Fetch, or both XHR and Fetch?
- how the integration should be done?

Thanks


[1] https://github.com/whatwg/streams
[2] http://xhr.spec.whatwg.org/
[3]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/core/streams/
[4] https://github.com/tyoshino/streams_integration/blob/master/README.md
[5] http://fetch.spec.whatwg.org/#fetch-method
[6] http://fetch.spec.whatwg.org/#body-stream-concept
[7]
https://groups.google.com/a/chromium.org/d/msg/blink-dev/GoFbe0yLO50/SXpYMdYn0A4J
[8]
https://groups.google.com/a/chromium.org/d/msg/blink-dev/GoFbe0yLO50/vviGEQ5Z-KoJ