[Media Router] Assign each route a current cast mode if possible

chrome/browser/resources/media_router/media_router_data.js

Index: chrome/browser/resources/media_router/media_router_data.js
diff --git a/chrome/browser/resources/media_router/media_router_data.js b/chrome/browser/resources/media_router/media_router_data.js
index 93cced02f708a153c1b2636c88f21cb7ce5178c3..7e3897001faf7615ccf2d470612ba420de1c7f3a 100644
--- a/chrome/browser/resources/media_router/media_router_data.js
+++ b/chrome/browser/resources/media_router/media_router_data.js
@@ -198,6 +198,9 @@ cr.define('media_router', function() {
     /** @type {boolean} */
     this.canJoin = canJoin;
 
+    /** @type {number|undefined} */
+    this.currentCastMode = undefined;
+
     /** @type {?string} */
     this.customControllerPath = customControllerPath;
   };