[sensors] What are the event.type strings?

martijnthe has just created a new issue for https://github.com/w3c/sensors:

== What are the event.type strings? ==
I looking at the [test suite] in the hope of finding out answers but, I don't see `sensor.addEventListener(...)` being used there...

There was some discussion [here], but it's unclear to me from the spec doc what various the `Event`'s `type` strings are supposed to be. In case one wants to use the `EventTarget` interface instead of the `onreading`, etc. properties this is quite important 😄 It would be nice if this could be documented more clearly and also be added to the test cases.

cc @jiangzidong

[here]: https://github.com/w3c/sensors/issues/205
[test suite]: https://github.com/w3c/web-platform-tests/blob/master/generic-sensor/generic-sensor-tests.js

Please view or discuss this issue at https://github.com/w3c/sensors/issues/245 using your GitHub account