[Media Router WebUI] Remove unnecessary default property values.

chrome/browser/resources/media_router/elements/route_details/route_details.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.
 
 // This Polymer element shows information from media that is currently cast
 // to a device.
 Polymer({
   is: 'route-details',
 
   properties: {
     /**
      * The text for the current casting activity status.
-     * @private {string}
+     * @private {string|undefined}
      */
     activityStatus_: {
       type: String,
-      value: '',
     },
 
     /**
      * Whether the browser is currently incognito.
-     * @type {boolean}
+     * @type {boolean|undefined}
      */
     isOffTheRecord: {
       type: Boolean,
-      value: false,
     },
 
     /**
      * The route to show.
-     * @type {?media_router.Route}
+     * @type {?media_router.Route|undefined}
      */
     route: {
       type: Object,
-      value: null,
       observer: 'maybeLoadCustomController_',
     },
 
     /**
      * Whether the custom controller should be hidden.
      * A custom controller is shown iff |route| specifies customControllerPath
      * and the view can be loaded.
      * @private {boolean}
      */
     isCustomControllerHidden_: {
@@ skipping 57 matching lines @@
     extensionview.load(this.route.customControllerPath)
     .then(function() {
       // Load was successful; show the custom controller.
       that.isCustomControllerHidden_ = false;
     }, function() {
       // Load was unsuccessful; fall back to default view.
       that.isCustomControllerHidden_ = true;
     });
   },
 });