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

chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js

Index: chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js
diff --git a/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js b/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js
index 26362e10a694143a51d0fba9b523a486a1fd99af..c7065c5fce1341f0701b0630c4949601749baea8 100644
--- a/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js
+++ b/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js
@@ -360,6 +360,16 @@ Polymer({
     },
 
     /**
+     * ID of the sink waiting for the current route to it to be closed so a new
+     * one can be started, or the empty string when no such sink is waiting.
+     * @private {string}
+     */
+    sinkIdAwaitingNewRoute_: {
+      type: String,
+      value: '',
+    },
+
+    /**
      * Max height for the sink list.
      * @private {number}
      */
@@ -1571,6 +1581,25 @@ Polymer({
   },
 
   /**
+   * Handles a cast-new-media-click event. Closes the currently displayed local
+   * route and shows the sink list. When the current route has been successfully
+   * removed from the route map, the container will launch a new route for the
+   * same sink.
+   *
+   * @param {!Event} event The event object.
+   * Parameters in |event|.detail:
+   *   route - route to close.
+   * @private
+   */
+  onCastNewMediaClick_: function(event) {
+    /** @type {{route: !media_router.Route}} */
+    var detail = event.detail;
+    this.sinkIdAwaitingNewRoute_ = detail.route.sinkId;
+    this.fire('close-route-for-new-media', detail);
+    this.showSinkList_();
+  },
+
+  /**
    * Handles a close-route-click event. Shows the sink list and starts a timer
    * to close the dialog if there is no click within three seconds.
    *
@@ -1936,6 +1965,15 @@ Polymer({
 
     this.sinkToRouteMap_ = tempSinkToRouteMap;
     this.rebuildSinksToShow_();
+
+    // A sink was waiting for its route to be closed and removed from the route
+    // map so a new route to it can be started.
+    if (this.sinkIdAwaitingNewRoute_ != '' &&
+        !(this.sinkIdAwaitingNewRoute_ in this.sinkToRouteMap_) &&
+        this.sinkIdAwaitingNewRoute_ in this.sinkMap_) {
+      this.showOrCreateRoute_(this.sinkMap_[this.sinkIdAwaitingNewRoute_]);
+      this.sinkIdAwaitingNewRoute_ = '';
+    }
   },
 
   /**