[MediaRouter UI] Compile MR WebUI js code with Closure.

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: {
@@ skipping 26 matching lines @@
       value: loadTimeData.getString('joinButton'),
     },
 
     /**
      * The text for the stop casting button.
      * @private {string}
      */
     stopCastingButtonText_: {
       type: String,
       readOnly: true,
-      value: loadTimeData.getString('stopCastingButton'),
+      value: function() {
+        return loadTimeData.getString('stopCastingButton');
+      },
     },
 
     /**
      * 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_: {
       type: Boolean,
@@ skipping 51 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;
     });
   },
 });