[ServiceWorker] Update .focus() to return a WindowClient instead of bool.

Source/modules/serviceworkers/ServiceWorkerWindowClient.h

Index: Source/modules/serviceworkers/ServiceWorkerWindowClient.h
diff --git a/Source/modules/serviceworkers/ServiceWorkerWindowClient.h b/Source/modules/serviceworkers/ServiceWorkerWindowClient.h
index 57feb92377f080227c562287cef10d3b97c73085..332589193e27f7155692177cee794f66fe97f8c6 100644
--- a/Source/modules/serviceworkers/ServiceWorkerWindowClient.h
+++ b/Source/modules/serviceworkers/ServiceWorkerWindowClient.h
@@ -12,11 +12,18 @@
 
 namespace blink {
 
+class ScriptPromiseResolver;
 class ScriptState;
 
 class ServiceWorkerWindowClient final : public ServiceWorkerClient {
     DEFINE_WRAPPERTYPEINFO();
 public:
+    // To be used by CallbackPromiseAdapter.
+    typedef WebServiceWorkerClientInfo WebType;
+
+    static ServiceWorkerWindowClient* take(ScriptPromiseResolver*, WebType*);
+    static void dispose(WebType*);
+
     static ServiceWorkerWindowClient* create(const WebServiceWorkerClientInfo&);
     ~ServiceWorkerWindowClient() override;