Define service worker events (#1452)

This introduces the concept, service worker events, to refer to the events that
are one of lifecycle events, functional events, and the legacy message events
dispatched to ServiceWorkerGlobalScope.

Related PR: whatwg/dom#653.

docs/index.bs

@@ -193,7 +193,10 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
     <section>
       <h4 id="service-worker-events">Events</h4>
 
-      Service Workers specification defines <dfn export id="dfn-lifecycle-events">lifecycle events</dfn> (each of which is an [=event=]), {{install!!event}} and {{activate!!event}}. Service Workers and other specifications that <a href="#extensibility">extend</a> Service Workers define set of events called <dfn export id="dfn-functional-events">functional events</dfn> (each of which is an [=event=]) including {{fetch!!event}}. (See the <a href="#execution-context-events">list</a> of [=lifecycle events=] and [=functional events=].)
+      The Service Workers specification defines <dfn export id="dfn-service-worker-events">service worker events</dfn> (each of which is an [=event=]) that include (see the <a href="#execution-context-events">list</a>):
+          * <dfn export id="dfn-lifecycle-events">Lifecycle events</dfn>: {{install!!event}} and {{activate!!event}}.
+          * <dfn export id="dfn-functional-events">Functional events</dfn>: {{fetch!!event}} and the [=events=] defined by other specifications that <a href="#extensibility">extend</a> the Service Workers specification. (See the <a href="#execution-context-events">list</a>.)
+          * {{message!!event}} and {{messageerror!!event}}.
     </section>
   </section>
 
@@ -1613,7 +1616,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
   <section>
     <h3 id="execution-context-events">Events</h3>
 
-    The following events are dispatched on {{ServiceWorkerGlobalScope}} object:
+    The following events, called [=service worker events=], are dispatched on {{ServiceWorkerGlobalScope}} object:
 
     <table class="data" dfn-for="ServiceWorkerGlobalScope">
       <thead>

docs/v1/index.bs

@@ -182,7 +182,10 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
     <section>
       <h4 id="service-worker-events">Events</h4>
 
-      Service Workers specification defines <dfn export id="dfn-lifecycle-events">lifecycle events</dfn> (each of which is an [=event=]), {{install!!event}} and {{activate!!event}}. Service Workers and other specifications that <a href="#extensibility">extend</a> Service Workers define set of events called <dfn export id="dfn-functional-events">functional events</dfn> (each of which is an [=event=]) including {{fetch!!event}}. (See the <a href="#execution-context-events">list</a> of [=lifecycle events=] and [=functional events=].)
+      The Service Workers specification defines <dfn export id="dfn-service-worker-events">service worker events</dfn> (each of which is an [=event=]) that include (see the <a href="#execution-context-events">list</a>):
+          * <dfn export id="dfn-lifecycle-events">Lifecycle events</dfn>: {{install!!event}} and {{activate!!event}}.
+          * <dfn export id="dfn-functional-events">Functional events</dfn>: {{fetch!!event}} and the [=events=] defined by other specifications that <a href="#extensibility">extend</a> the Service Workers specification. (See the <a href="#execution-context-events">list</a>.)
+          * {{message!!event}} and {{messageerror!!event}}.
     </section>
   </section>
 
@@ -1493,7 +1496,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
   <section>
     <h3 id="execution-context-events">Events</h3>
 
-    The following events are dispatched on {{ServiceWorkerGlobalScope}} object:
+    The following events, called [=service worker events=], are dispatched on {{ServiceWorkerGlobalScope}} object:
 
     <table class="data" dfn-for="ServiceWorkerGlobalScope">
       <thead>
@@ -2354,7 +2357,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
               <p>Note: This step has two known issues.</p>
               <p>First, using the to-be-created [=environment settings object=] rather than a concrete [=environment settings object=]. This is used due to the unique processing model of service workers compared to the processing model of other [=web workers=]. The script fetching algorithms of HTML standard originally designed for other [=web workers=] require an [=environment settings object=] of the execution environment, but service workers fetch a script separately in the [=Update=] algorithm before the script later runs multiple times through the [=Run Service Worker=] algorithm.</p>
               <p>Second, the [=fetch a classic worker script=] algorithm and the [=fetch a module worker script graph=] algorithm in HTML take |job|’s [=job/client=] as an argument. |job|’s [=job/client=] is null when passed from the [=Soft Update=] algorithm.</p>
-              <p>These issues are tracked in the [issue #1013](https://github.com/w3c/ServiceWorker/issues/1013) of the ServiceWorkers GitHub repository. We will address these issues in [Service Workers Nightly](https://w3c.github.io/ServiceWorker/).</p>
+              <p>These issues are tracked in the [issue #1013](https://github.com/w3c/ServiceWorker/issues/1013) of the Service Workers GitHub repository. We will address these issues in [Service Workers Nightly](https://w3c.github.io/ServiceWorker/).</p>
           </div>
 
           To [=fetching scripts/perform the fetch=] given |request|, run the following steps: