Update ServiceWorker event handled status histogram

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 ea110b9d7b4be2b0f7cfa6091f0e96200de9f0d0..41f61642972be7dcb23c55f829e80ef7f1668fdf 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -37509,6 +37509,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ServiceWorker.EventHandledRatioType.Fetch"
+    enum="ServiceWorkerEventHandleRatioType">
+  <owner>kinuko@chromium.org</owner>
+  <summary>
+    Records how much of fetch events are handled compared with the number of

[Ilya Sherman, 2015/07/06 18:44:50]

nit: "how much of" -> "how many"

[kinuko, 2015/07/07 08:31:39]

Done.

+    events that are fired for a ServiceWorker.  Recorded each time the
+    ServiceWorker is stopped.
+  </summary>
+</histogram>
+
 <histogram name="ServiceWorker.FetchEvent.MainResource.Status"
     enum="ServiceWorkerStatusCode">
   <owner>falken@chromium.org</owner>
@@ -37744,6 +37754,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="ServiceWorker.UnhandledEventRatio" units="percent">
   <owner>kinuko@chromium.org</owner>
+  <obsolete>
+    Deprecated 2015-06 in favor of ServiceWorker.EventHandledStatus*.
+  </obsolete>
   <summary>
     Records the ratio of unhandled events to all events that are dispatched to
     each ServiceWorker.  Recorded when each ServiceWorkerVersion is destructed.
@@ -66336,6 +66349,12 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="2" label="MIGRATION_ERROR_FAILED"/>
 </enum>
 
+<enum name="ServiceWorkerEventHandleRatioType" type="int">
+  <int value="0" label="ALL_EVENTS_HANDLED"/>
+  <int value="1" label="SOME_EVENTS_HANDLED"/>
+  <int value="2" label="NO_EVENTS_HANDLED"/>

[Ilya Sherman, 2015/07/06 18:44:50]

nit: I'd use shorter labels, like "All", "Some", and "None".  Or, if you prefer
the more explicit longer labels, I'd at least recommend writing them in a more
human-friendly way, e.g. "All events handled"

[kinuko, 2015/07/07 08:31:39]

Done.

+</enum>
+
 <enum name="ServiceWorkerReadResponseResult" type="int">
   <int value="0" label="OK"/>
   <int value="1" label="Read headers error"/>