Re: [whatwg/dom] Change add/remove event listener behavior for service workers (#653)

jungkees commented on this pull request.



> -  <p class="note no-backref">To optimize storing the event types allowed for the service worker and
-  to avoid non-deterministic changes to the event listeners, invocation of the method is allowed
-  only during the very first evaluation of the service worker script.
+  <p>If <var>listener</var> observes a <a>functional event</a>, <var>eventTarget</var> is a
+  {{ServiceWorkerGlobalScope}} object, and its associated <a>service worker</a>'s <a for="service
+  worker">script resource</a>'s <a for="script resource">has ever been evaluated flag</a> is set,
+  then the user agent must <a>report a warning to the console</a> with a description that explains
+  that the user agent stores the event <a for="event listener">type</a> of the <a>functional
+  event</a> for the <a>service worker</a> only during the very first evalution of the <a>service
+  worker</a> script, and the asynchronously added <a>functional event</a> will not start the
+  <a>service worker</a>. [[!SERVICE-WORKERS]]
+
+  <p class="note no-backref">To optimize storing the event types allowed for the <a>service
+  worker</a>, Service Workers specification does not store the asynchronously added event <a
+  for="event listener">type</a>. The <a>event listener</a> will still be added under this condition,
+  but the implmentations have to inform developers about this behavior.

I guess this note would help implementers understand *why* this behavior was added (while the warning description says what to display to the console as you pointed). I tried to simplify the words.

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