Allow Blink to respond asynchronously to SW Push events (side 2/3)

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 e4a7f32fed23e1de0478aa4edaaecfa95ab82162..19dc42267bdbfc224cf41dea85bc242b4585df12 100644
--- a/Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h
+++ b/Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h
@@ -63,6 +63,7 @@ public:
     // provided by the service worker in the fetch events, so fallback to native.
     virtual void didHandleFetchEvent(int fetchEventID) = 0;
     virtual void didHandleFetchEvent(int fetchEventID, const WebServiceWorkerResponse&) = 0;
+    virtual void didHandlePushEvent(int pushEventID, WebServiceWorkerEventResult) = 0;
     virtual void didHandleSyncEvent(int syncEventID) = 0;
     virtual void postMessageToClient(int clientID, const WebString& message, PassOwnPtr<WebMessagePortChannelArray>) = 0;