Re: [sensors] Use simple event dispatch mechanism instead of task source (queued)

So definitive feedback from WHATWG folks is roughly to write:

```
1.  [=In parallel=], wait for a a new reading to be available.
    When it is, [=queue a task=] to run the following sub-steps:
    1.  If [[unsecure_stuff_happening]] flag is set, then return.
    1.  Update the [=latest reading=] map.
    1.  Copy to instance cache if that's what we end-up choosing to do.
    1.  Fire a "change" event.
```

So we can get rid of the custom task queue, but not of task queues altogether.

-- 
GitHub Notification of comment by tobie
Please view or discuss this issue at https://github.com/w3c/sensors/issues/215#issuecomment-304374993 using your GitHub account