Add DiscoveryNetworkMonitor implementation

chrome/test/data/extensions/api_test/dial/experimental/get_network_id.js

Index: chrome/test/data/extensions/api_test/dial/experimental/get_network_id.js
diff --git a/chrome/test/data/extensions/api_test/dial/experimental/get_network_id.js b/chrome/test/data/extensions/api_test/dial/experimental/get_network_id.js
new file mode 100644
index 0000000000000000000000000000000000000000..89993bfaa09b95c23b5252f77cd7cb08cf772cfd
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/dial/experimental/get_network_id.js
@@ -0,0 +1,11 @@
+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+chrome.dial.getNetworkId(networkId => {
+  chrome.test.assertFalse(networkId == "disconnected");
+  chrome.test.assertFalse(networkId == "unknown");
+  chrome.test.succeed();
+});
+
+chrome.test.notifyPass();