Add custom Polymer network icon element

ui/webui/resources/cr_elements/cr_network_icon/cr_network_icon_externs.js

+// Copyright 2015 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.
+
+// TODO(jlklein/stevenjb): Delete this once auto generated.
+
+/**
+ * @fileoverview Closure compiler externs for CrNetworkIconElement.
+ *
+ * @externs
+ */
+
+/** @constructor @extends {HTMLElement} */
+var CrNetworkIconElement = function() {};
+
+
+/** @type {CrOncDataElement} */
+CrNetworkIconElement.prototype.networkState;
+
+
+/** @type {CrOnc.Type} */
+CrNetworkIconElement.prototype.networkType;
+
+
+/** @type {boolean} */
+CrNetworkIconElement.prototype.isListItem;