service worker: Attribute purpose to start worker attempts for UMA

content/browser/service_worker/service_worker_context_wrapper.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/service_worker/service_worker_context_wrapper.h"
 
 #include <map>
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 44 matching lines @@
 void StartActiveWorkerOnIO(
     const ServiceWorkerContextWrapper::StatusCallback& callback,
     ServiceWorkerStatusCode status,
     const scoped_refptr<ServiceWorkerRegistration>& registration) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (status == SERVICE_WORKER_OK) {
     // Pass the reference of |registration| to WorkerStarted callback to prevent
     // it from being deleted while starting the worker. If the refcount of
     // |registration| is 1, it will be deleted after WorkerStarted is called.
     registration->active_version()->StartWorker(
+        ServiceWorkerMetrics::EventType::UNKNOWN,
         base::Bind(WorkerStarted, callback));
     return;
   }
   BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                           base::Bind(callback, SERVICE_WORKER_ERROR_NOT_FOUND));
 }
 
 }  // namespace
 
 void ServiceWorkerContext::AddExcludedHeadersForFetchEvent(
@@ skipping 645 matching lines @@
   observer_list_->Notify(FROM_HERE,
                          &ServiceWorkerContextObserver::OnStorageWiped);
 }
 
 ServiceWorkerContextCore* ServiceWorkerContextWrapper::context() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   return context_core_.get();
 }
 
 }  // namespace content