ServiceWorkerContainer spec lists `onerror` as an event handler

[tony19]

I think the ServiceWorkerContainer spec should not list event handlers.

Service Workers 1 and MDN list onerror as an attribute of ServiceWorkerContainer. My tests show that Chrome 51/53, Firefox 47, and Opera 38/39 do not actually support navigator.serviceWorker.onerror, contrary to the Browser Compatibility table in MDN; and that onerror is only available from within a service worker object.

I later discovered a comment in #199 from @jakearchibald and a comment in #198 from @kinu that indicate onerror was moved from the container, so I'm assuming the ServiceWorkerContainer spec just needs to be updated. Correct?

StackOverflow ref

[wanderview]

I can't find any place we fire this error event in gecko. Are we sure no other specs like push or background sync use it, though?

[makotoshimazu]

FYI: Blink looks the same with gecko. onerror isn't defined at the idl file, and I couldn't find any log that onerror has been implemented.

[jakearchibald]

Pre F2F notes: Seems like this is a hangover from early API sketches. Probably should be removed. We should come up with a plan for error handling.

[jakearchibald]

F2F: We should remove this

[slightlyoff]

LGTM.