Use UUID for ServiceWorker Client identifier (1/3, blink)

Source/modules/serviceworkers/ServiceWorkerWindowClient.cpp

Index: Source/modules/serviceworkers/ServiceWorkerWindowClient.cpp
diff --git a/Source/modules/serviceworkers/ServiceWorkerWindowClient.cpp b/Source/modules/serviceworkers/ServiceWorkerWindowClient.cpp
index 8712916a69f3f8ec5659512b2144642f6ce16d1e..604af9998a4c02643dd0a5d871ec41b310ea103e 100644
--- a/Source/modules/serviceworkers/ServiceWorkerWindowClient.cpp
+++ b/Source/modules/serviceworkers/ServiceWorkerWindowClient.cpp
@@ -77,7 +77,12 @@ ScriptPromise ServiceWorkerWindowClient::focus(ScriptState* scriptState)
     }
     scriptState->executionContext()->consumeWindowInteraction();
 
-    ServiceWorkerGlobalScopeClient::from(scriptState->executionContext())->focus(id(), new CallbackPromiseAdapter<ServiceWorkerWindowClient, ServiceWorkerError>(resolver));
+    if (!uuid().isEmpty()) {
+        ServiceWorkerGlobalScopeClient::from(scriptState->executionContext())->focus(uuid(), new CallbackPromiseAdapter<ServiceWorkerWindowClient, ServiceWorkerError>(resolver));
+    } else {
+        // FIXME: Deprecate this when we switch to uuid.
+        ServiceWorkerGlobalScopeClient::from(scriptState->executionContext())->focus(id(), new CallbackPromiseAdapter<ServiceWorkerWindowClient, ServiceWorkerError>(resolver));
+    }
     return promise;
 }