Populate .current when navigator.serviceWorker is accessed

content/common/service_worker/service_worker_messages.h

Index: content/common/service_worker/service_worker_messages.h
diff --git a/content/common/service_worker/service_worker_messages.h b/content/common/service_worker/service_worker_messages.h
index 8af1825e7e994c26dee0cd6dc146b22cc4c193fc..5337c6b9dde98580c0883f167ea915ba91f078f8 100644
--- a/content/common/service_worker/service_worker_messages.h
+++ b/content/common/service_worker/service_worker_messages.h
@@ -81,8 +81,12 @@ IPC_MESSAGE_CONTROL1(ServiceWorkerHostMsg_ProviderCreated,
 IPC_MESSAGE_CONTROL1(ServiceWorkerHostMsg_ProviderDestroyed,
                      int /* provider_id */)
 
-// Informs the browser of a ServiceWorker object being destroyed.
-IPC_MESSAGE_CONTROL1(ServiceWorkerHostMsg_ServiceWorkerObjectDestroyed,
+// Increments and decrements the ServiceWorker object's reference
+// counting in the browser side. The ServiceWorker object is created
+// with ref-count==1 initially.
+IPC_MESSAGE_CONTROL1(ServiceWorkerHostMsg_IncrementServiceWorkerRefCount,
+                     int /* handle_id */)
+IPC_MESSAGE_CONTROL1(ServiceWorkerHostMsg_DecrementServiceWorkerRefCount,
                      int /* handle_id */)
 
 // Informs the browser that |provider_id| is associated
@@ -92,16 +96,6 @@ IPC_MESSAGE_CONTROL2(ServiceWorkerHostMsg_SetVersionId,
                      int /* provider_id */,
                      int64 /* version_id */)
 
-// Informs the browser of a new scriptable API client in the child process.
-IPC_MESSAGE_CONTROL2(ServiceWorkerHostMsg_AddScriptClient,
-                     int /* thread_id */,
-                     int /* provider_id */)
-
-// Informs the browser that the scriptable API client is unregistered.
-IPC_MESSAGE_CONTROL2(ServiceWorkerHostMsg_RemoveScriptClient,
-                     int /* thread_id */,
-                     int /* provider_id */)
-
 // Informs the browser that event handling has finished.
 // Routed to the target ServiceWorkerVersion.
 IPC_MESSAGE_ROUTED2(ServiceWorkerHostMsg_InstallEventFinished,