[MediaRouter] Update MR-2-Extension's PostMessage to return boolean.

extensions/renderer/resources/media_router_bindings.js

Index: extensions/renderer/resources/media_router_bindings.js
diff --git a/extensions/renderer/resources/media_router_bindings.js b/extensions/renderer/resources/media_router_bindings.js
index f28c354d2df7241a7ed0571a243be1b7e2a13884..cc7bdacdb07dec64b7328b5754b36380a5c0b9c7 100644
--- a/extensions/renderer/resources/media_router_bindings.js
+++ b/extensions/renderer/resources/media_router_bindings.js
@@ -449,11 +449,18 @@ define('media_router_bindings', [
    * @param {!string} routeId
    * @param {!string} message
    * @param {string} extraInfoJson
+   * @return {!Promise.<boolean>} Resolved with true if the message was sent,
+   *  or false on failure.
    */
   MediaRouter.prototype.postMessage = function(
       routeId, message, extraInfoJson) {
     // TODO(mfoltz): Remove extraInfoJson if no longer needed.

[mark a. foltz, 2015/06/11 05:04:29]

Is it possible to take care of this now?

[haibinlu, 2015/06/11 17:37:17]

Done.

-    this.handlers_.postMessage(routeId, message, JSON.parse(extraInfoJson));
+    this.handlers_.postMessage(routeId, message, JSON.parse(extraInfoJson))
+        .then(function() {
+          return true;
+        }, function() {
+          return false;
+        });
   };
 
   /**