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 avoid unnecessary delays, Service Workers [[!SERVICE-WORKERS]]
-  permits skipping event dispatch when no <a>event listeners</a> for the <a>service worker event</a>
-  have been deterministically added in the <a>service worker</a>’s <a for="service worker">set of
-  event types to handle</a> during the very first script evaluation. The <a>event listener</a> in
-  this step will still be added, but the implementations have to inform developers about this
-  behavior.
+  <p>If <var>eventTarget</var> is a {{ServiceWorkerGlobalScope}} object, its
+  <a for="ServiceWorkerGlobalScope">service worker</a>'s
+  <a for="service worker">script resource</a>'s
+  <a for="script resource">has ever been evaluated flag</a> is set, and <var>listener</var>'s
+  <a for="event listener">type</a> matches the {{Event/type}} attribute value of any of the
+  <a>service worker events</a>, then <a>report a warning to the console</a> that this might not give
+  the expected results. [[!SERVICE-WORKERS]]
+
+  <p class="note no-backref">Service workers are only started for event listeners added during the
+  first script evaluation.

We have an occasion that is not covered by this note. Service Workers changed the skipping behavior to optional: https://w3c.github.io/ServiceWorker/#should-skip-event-algorithm step 1 uses "may". So, the listeners added after the first script evaluation still can see the service worker starts. Should we say: "Service workers may only be started for event listeners added during the first script evaluation?"

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