[push-api] Mention what to do in register() and getRegistration() if there is no active SW (#100)

Chromium implementation throws an exception. I'm not sure if that's something we can actually hit.

@mvano ?

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/push-api/issues/100

Received on Thursday, 18 December 2014 15:09:16 UTC