Implement the ServiceWorker "activate" event during activation

content/browser/service_worker/service_worker_version.cc

Index: content/browser/service_worker/service_worker_version.cc
diff --git a/content/browser/service_worker/service_worker_version.cc b/content/browser/service_worker/service_worker_version.cc
index be530d453cc9805ad03e4dcdb6aa7f55c57ea77b..2de6c80ae572d6cda41996c578358b0f25884800 100644
--- a/content/browser/service_worker/service_worker_version.cc
+++ b/content/browser/service_worker/service_worker_version.cc
@@ -306,20 +306,19 @@ void ServiceWorkerVersion::DispatchActivateEvent(
     const StatusCallback& callback) {
   DCHECK_EQ(INSTALLED, status()) << status();
   SetStatus(ACTIVATING);
-  // TODO(kinuko): Implement.
-  NOTIMPLEMENTED();
+  // TODO(dominicc): Also dispatch activate callbacks to the document,
+  // and activate end callbacks to the service worker and the document.
   HandleInstallPhaseEventFinishedParameters params(
       weak_factory_.GetWeakPtr(),
-      -1 /* dummy message_id */,
-      InstallPhaseEventFinishedMessageReader(),
+      ServiceWorkerHostMsg_ActivateEventFinished::ID,
+      base::Bind(&ServiceWorkerHostMsg_ActivateEventFinished::Read),
       callback,
       ACTIVE,
       INSTALLED,
       SERVICE_WORKER_ERROR_ACTIVATE_WORKER_FAILED);
-  RunSoon(base::Bind(&HandleInstallPhaseEventFinished,
-                     params,
-                     SERVICE_WORKER_OK,
-                     IPC::Message(-1, -1, IPC::Message::PRIORITY_NORMAL)));
+  SendMessageAndRegisterCallback(
+      ServiceWorkerMsg_ActivateEvent(),
+      base::Bind(&HandleInstallPhaseEventFinished, params));
 }
 
 void ServiceWorkerVersion::DispatchFetchEvent(