Added an adapter.

Change-Id: Iac04d196099e72ddbb1d5b29ecb6bc0f1e0f5c18

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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.
+ */
+package org.onosproject.ui;
+
+import java.util.List;
+
+/**
+ * Adapter for testing against UI extension service.
+ */
+public class UiExtensionServiceAdapter implements UiExtensionService {
+    @Override
+    public void register(UiExtension extension) {
+    }
+
+    @Override
+    public void unregister(UiExtension extension) {
+    }
+
+    @Override
+    public List<UiExtension> getExtensions() {
+        return null;
+    }
+
+    @Override
+    public UiExtension getViewExtension(String viewId) {
+        return null;
+    }
+}