GUI2 added in the layout topo overlay

Change-Id: I9960f95ae726a5af9950771ed67bcfc9d172e267
diff --git a/web/gui2-topo-lib/projects/gui2-topo-lib/src/lib/layout.service.ts b/web/gui2-topo-lib/projects/gui2-topo-lib/src/lib/layout.service.ts
new file mode 100644
index 0000000..2ed795a
--- /dev/null
+++ b/web/gui2-topo-lib/projects/gui2-topo-lib/src/lib/layout.service.ts
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { Injectable } from '@angular/core';
+import {LogService, WebSocketService} from 'gui2-fw-lib';
+
+export enum LayoutType {
+    LAYOUT_DEFAULT = 'default',
+    LAYOUT_ACCESS = 'access'
+}
+
+/**
+ * ONOS GUI - Layout service - connects to the Layout UI Extension app
+ */
+@Injectable()
+export class LayoutService {
+
+    constructor(
+        protected log: LogService,
+        protected wss: WebSocketService
+    ) {
+        this.log.debug('LayoutService constructed');
+    }
+
+    /**
+     * tell the server we want a new layout
+     * @param type The type of layout we want
+     */
+    changeLayout(type: LayoutType): void {
+        this.wss.sendEvent('doLayout', {
+            type: type
+        });
+        this.log.debug('Layout changed to', type);
+    }
+}