The blink half of the new ServiceWorker 'sync' event.

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 5deb2252a8e189e8af5ef146b52eee2e68ba9485..d8e0343282062b817f6695c2814e0382e3d49747 100644
--- a/Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h
+++ b/Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.h
@@ -50,6 +50,7 @@ public:
     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;
+    virtual void didHandleSyncEvent(int syncEventID) = 0;
 
     static const char* supplementName();
     static ServiceWorkerGlobalScopeClient* from(ExecutionContext*);