Populate .current when navigator.serviceWorker is accessed

content/browser/service_worker/service_worker_handle.cc

Index: content/browser/service_worker/service_worker_handle.cc
diff --git a/content/browser/service_worker/service_worker_handle.cc b/content/browser/service_worker/service_worker_handle.cc
index cc57b6fa3fdf518d397e55d7a42c35d0867f817d..a07ab9e9d91004a287e849859f4f9d8cff46818d 100644
--- a/content/browser/service_worker/service_worker_handle.cc
+++ b/content/browser/service_worker/service_worker_handle.cc
@@ -63,6 +63,7 @@ ServiceWorkerHandle::ServiceWorkerHandle(
       sender_(sender),
       thread_id_(thread_id),
       handle_id_(context.get() ? context->GetNewServiceWorkerHandleId() : -1),
+      ref_count_(1),
       registration_(registration),
       version_(version) {
   version_->AddListener(this);
@@ -112,4 +113,14 @@ ServiceWorkerObjectInfo ServiceWorkerHandle::GetObjectInfo() {
   return info;
 }
 
+void ServiceWorkerHandle::IncrementRefCount() {
+  DCHECK_GT(ref_count_, 0);
+  ++ref_count_;
+}
+
+void ServiceWorkerHandle::DecrementRefCount() {
+  DCHECK_GE(ref_count_, 0);
+  --ref_count_;
+}
+
 }  // namespace content