service worker: Attribute purpose to start worker attempts for UMA

content/browser/service_worker/service_worker_register_job.cc

Index: content/browser/service_worker/service_worker_register_job.cc
diff --git a/content/browser/service_worker/service_worker_register_job.cc b/content/browser/service_worker/service_worker_register_job.cc
index ae7b436b00946fad25eec26ecf8bc2ed60f85b12..3e326fbbebb51abb97d5874305fc86dd42dffba1 100644
--- a/content/browser/service_worker/service_worker_register_job.cc
+++ b/content/browser/service_worker/service_worker_register_job.cc
@@ -417,7 +417,8 @@ void ServiceWorkerRegisterJob::InstallAndContinue() {
       base::Bind(&ServiceWorkerRegisterJob::DispatchInstallEvent,
                  weak_factory_.GetWeakPtr()),
       base::Bind(&ServiceWorkerRegisterJob::OnInstallFinished,
-                 weak_factory_.GetWeakPtr()));
+                 weak_factory_.GetWeakPtr()),
+      ServiceWorkerMetrics::EventType::INSTALL);
 
   // A subsequent registration job may terminate our installing worker. It can
   // only do so after we've started the worker and dispatched the install