ServiceWorker: Keep the worker alive until FetchEvent.waitUntil settles

content/browser/service_worker/service_worker_metrics.h

Index: content/browser/service_worker/service_worker_metrics.h
diff --git a/content/browser/service_worker/service_worker_metrics.h b/content/browser/service_worker/service_worker_metrics.h
index 9be6cdb4a5147ff15ca6a9d2c40d4e7da42ee362..d4aa155c0f4f824534e07c18e43f94cae24054b0 100644
--- a/content/browser/service_worker/service_worker_metrics.h
+++ b/content/browser/service_worker/service_worker_metrics.h
@@ -97,6 +97,7 @@ class ServiceWorkerMetrics {
     FETCH_SUB_RESOURCE = 13,
     UNKNOWN = 14,  // Used when event type is not known.
     FOREIGN_FETCH = 15,
+    FETCH_WAITUNTIL = 16,
     // Add new events to record here.
     NUM_TYPES
   };