service worker: Avoid starting up for activation during shutdown

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index e27be831c1d97deee5003d779751ae1067c2dc53..edf00b0065f911de3bb7628759bbd936888d0ac2 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -96697,6 +96697,12 @@ To add a new entry, add it with any value and run test to compute valid value.
   <suffix name="3" label="Failed three times."/>
 </histogram_suffixes>
 
+<histogram_suffixes name="ServiceWorker.ShutdownStatus">
+  <affected-histogram name="ServiceWorker.ActivateEventStatus"/>

[Mark P, 2016/06/01 21:10:42]

Please revise the histogram description to cover these new suffixes.  The
current description is "The result of dispatching the activate event to the
worker."  For the suffixes, this is clearly not still true.  Does _every_ result
of a dispatch event get sent to one of those two suffixed histograms?  If so,
then you can revise it by adding the following sentence:  "This is recorded to
both ServiceWorker.ActivateEventStatus and whichever of
ServiceWorker.ActivateEventStatus_InShutdown and
ServiceWorker.ActivateEventStatus_NotInShutdown is appropriate."  If not, then
you'll have to revise the description yourself.

[falken, 2016/06/02 07:12:33]

Done.

+  <suffix name="InShutdown" label="Browser shutdown started."/>
+  <suffix name="NotInShutdown" label="Browser shutdown has not started."/>
+</histogram_suffixes>
+
 <histogram_suffixes name="ServiceWorker.StartSituation">
   <affected-histogram name="EmbeddedWorkerInstance.Start.TimeToEvaluateScript"/>
   <affected-histogram name="EmbeddedWorkerInstance.Start.TimeToLoad.HttpCache"/>