[Media Router] Allow casting new media to sink with existing route.

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|undefined}
      */
     activityStatus_: {
       type: String,
     },
 
     /**
+     * Bitmask of available cast modes compatible with the sink of the current
+     * route.
+     * @type {number}
+     */
+    availableCastModes: {
+      type: Number,
+      value: 0,
+    },
+
+    /**
      * Whether the browser is currently incognito.
      * @type {boolean|undefined}
      */
     isOffTheRecord: {
       type: Boolean,
     },
 
     /**
      * The route to show.
      * @type {?media_router.Route|undefined}
@@ skipping 13 matching lines @@
       type: Boolean,
       value: true,
     },
   },
 
   behaviors: [
     I18nBehavior,
   ],
 
   /**
-   * Fires a close-route-click event. This is called when the button to close
+   * Fires a close-route 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});
+    this.fire('close-route', {route: this.route});
   },
 
   /**
-   * Fires a start-casting-to-route-click event. This is called when the button
-   * to start casting to the current route is clicked.
+   * @param {?media_router.Route|undefined} route
+   * @param {number} availableCastModes
+   * @return {boolean} Whether to show the button that allows casting to the
+   *     current route or the current route's sink.
+   */
+  computeCastButtonHidden_: function(route, availableCastModes) {
+    return !(route && route.canJoin) && !availableCastModes;
+  },
+
+  /**
+   * Fires a join-route-click event if the current route is joinable, otherwise
+   * it fires a cast-new-media-click event, which stops the current route and
+   * immediately launches a new route to the same sink. This is called when the
+   * button to start casting to the current route is clicked.
    *
    * @private
    */
   startCastingToRoute_: function() {
-    this.fire('start-casting-to-route-click', {route: this.route});
+    if (this.route.canJoin) {
+      this.fire('join-route-click', {route: this.route});
+    } else {
+      this.fire('cast-new-media-click', {route: this.route});
+    }
   },
 
   /**
    * Loads the custom controller if |route.customControllerPath| exists.
    * Falls back to the default route details view otherwise, or if load fails.
    * Updates |activityStatus_| for the default view.
    *
    * @private
    */
   maybeLoadCustomController_: function() {
@@ skipping 20 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;
     });
   },
 });