Dispatch the ServiceWorker "activate" event during activation

Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h

Index: Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h
diff --git a/Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h b/Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h
index d8e0343282062b817f6695c2814e0382e3d49747..4bcbbb3ee17b499da05f35befaeacf5c262ed22c 100644
--- a/Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h
+++ b/Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h
@@ -47,6 +47,7 @@ class ServiceWorkerGlobalScopeClient : public Supplement<WorkerClients> {
 public:
     virtual ~ServiceWorkerGlobalScopeClient() { }
 
+    virtual void didHandleActivateEvent(int eventID, blink::WebServiceWorkerEventResult) = 0;
     virtual void didHandleInstallEvent(int installEventID, blink::WebServiceWorkerEventResult) = 0;
     // A null response means no valid response was provided by the service worker, so fallback to native.
     virtual void didHandleFetchEvent(int fetchEventID, PassRefPtr<Response> = nullptr) = 0;