Implement the ServiceWorker "activate" event during activation

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 0c64a55f74a35f95ca63e0212ad42e3329a07613..354826a7d010a36f021616ff3bc30824c3bbee87 100644
--- a/content/common/service_worker/service_worker_messages.h
+++ b/content/common/service_worker/service_worker_messages.h
@@ -90,6 +90,9 @@ IPC_MESSAGE_CONTROL2(ServiceWorkerHostMsg_RemoveScriptClient,
 IPC_MESSAGE_CONTROL1(ServiceWorkerHostMsg_InstallEventFinished,
                      blink::WebServiceWorkerEventResult)
 
+IPC_MESSAGE_CONTROL1(ServiceWorkerHostMsg_ActivateEventFinished,
+                     blink::WebServiceWorkerEventResult);
+
 // Informs the browser that fetch event handling has finished.
 // Sent via EmbeddedWorker.
 IPC_MESSAGE_CONTROL2(ServiceWorkerHostMsg_FetchEventFinished,
@@ -120,6 +123,8 @@ IPC_MESSAGE_CONTROL4(ServiceWorkerMsg_ServiceWorkerRegistrationError,
 // Sent via EmbeddedWorker to dispatch install event.
 IPC_MESSAGE_CONTROL1(ServiceWorkerMsg_InstallEvent, int /* active_version_id */)
 
+IPC_MESSAGE_CONTROL0(ServiceWorkerMsg_ActivateEvent)
+
 // Sent via EmbeddedWorker to dispatch fetch event.
 IPC_MESSAGE_CONTROL1(ServiceWorkerMsg_FetchEvent,
                      content::ServiceWorkerFetchRequest)