add workerStart attribute to measure SW startup

Mirrors w3c/resource-timing#18

index.html

@@ -375,6 +375,9 @@ <h3>The <code>PerformanceNavigationTiming</code> interface</h3>
 with a time value equal to zero.</p>
 </dd>
 
+<dt>readonly attribute DOMHighResTimeStamp workerStart</dt>
+<dd>If the current document has an <a href="http://www.w3.org/TR/service-workers/#dfn-containing-service-worker-registration">active service worker registration</a> ([[!SERVICE-WORKERS]]), this atribute MUST return the time immediately before the user agent <a href="http://www.w3.org/TR/service-workers/#service-worker-concept">ran the worker</a> required to service the request, or if the worker was already available, the time immediately before the user agent <a href="http://www.w3.org/TR/service-workers/#on-fetch-request-algorithm">fired an event named `fetch`</a> at the <a href="http://www.w3.org/TR/service-workers/#dfn-active-worker">active worker</a>. Otherwise, if there is no active worker this attribute MUST return zero.</dd>
+
 <dt>readonly attribute DOMHighResTimeStamp linkNegotiationStart</dt>
 <dd>
 <p>This attribute is optional. User agents that don't have this attribute
@@ -882,8 +885,7 @@ <h3>Processing Model</h3>
     <a href="#widl-PerformanceNavigationTiming-unloadEventEnd">unloadEventEnd</a> to 0 then go to step
     <a href="#step-linknegotiation-start">9</a>. Otherwise, record <a href="#widl-PerformanceNavigationTiming-unloadEventEnd">unloadEventStart</a>
     as the time immediately before the unload event.</li>
-  <li>Immediately after the unload event is completed,
-    record the current time as <a href="#widl-PerformanceNavigationTiming-unloadEventEnd">unloadEventEnd</a>.</li>
+  <li>Immediately after the unload event is completed, record the current time as <a href="#widl-PerformanceNavigationTiming-unloadEventEnd">unloadEventEnd</a>. If the navigation URL has an <a href="http://www.w3.org/TR/service-workers/#dfn-active-worker">active worker registration</a>, immediately before the user agent <a href="http://www.w3.org/TR/service-workers/#service-worker-concept">runs the worker</a> record the time as <a href="#widl-PerformanceResourceTiming-workerStart">workerStart</a>, or if the worker is available, record the time before the <a href="http://www.w3.org/TR/service-workers/#on-fetch-request-algorithm">event named `fetch` is fired</a> at the active worker. Otherwise, if the navigation URL has no matching <a href="http://www.w3.org/TR/service-workers/#dfn-service-worker-registration">service worker registration</a>, set <a href="#widl-PerformanceResourceTiming-workerStart">workerStart</a> value to zero.</li>
   <li id="step-linknegotiation-start">If the navigation requires the network interface to be powered on or cycled, record the time immediately before doing that as <a href="#widl-PerformanceNavigationTiming-linkNegotiationStart">linkNegotiationStart</a>, and record the time immediately after the network interface becomes available as <a href="#widl-PerformanceNavigationTiming-linkNegotiationEnd">linkNegotiationEnd</a>. If the network interface was immediately available, let <a href="#widl-PerformanceNavigationTiming-linkNegotiationStart">linkNegotiationStart</a> and <a href="#widl-PerformanceNavigationTiming-linkNegotiationEnd">linkNegotiationEnd</a> be the same value as <a href="#widl-PerformanceNavigationTiming-startTime">startTime</a>.</li>
   <li id="step-fetch-start">If the new resource is to be fetched using HTTP GET
     or <a href="http://www.w3.org/TR/html5/infrastructure.html#concept-http-equivalent-get" title='HTTP GET method equivalence'>equivalent</a>,