[Media Router WebUI] Use I18nBehavior to retrieve strings.

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}
      */
     activityStatus_: {
       type: String,
       value: '',
     },
 
     /**
-     * The localized strings used by |this|.
-     * @private {!Object}
-     */
-    i18n_: {
-      readOnly: true,
-      type: Object,
-      value: function() {
-        var strings = {};
-        [
-          'startCastingButtonText',
-          'stopCastingButtonText',
-          'dropDownButtonTitle',
-        ]
-        .forEach(function(s) {
-          strings[s] = loadTimeData.getString(s);
-        });
-        return strings;
-      },
-    },
-
-    /**
      * The route to show.
      * @type {?media_router.Route}
      */
     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_: {
       type: Boolean,
       value: true,
     },
   },
 
+  behaviors: [
+    I18nBehavior,
+  ],
+
   /**
    * Fires a close-route-click event. This is called when the button to close
    * the current route is clicked.
    *
    * @private
    */
   closeRoute_: function() {
     this.fire('close-route-click', {route: this.route});
   },
 
@@ skipping 37 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;
     });
   },
 });