[Media Router] Adds return value to mojo MediaRouteProvider::TerminateRoute.

extensions/renderer/resources/media_router_bindings.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.
 
 var mediaRouter;
 
 define('media_router_bindings', [
     'mojo/public/js/bindings',
     'mojo/public/js/core',
     'content/public/renderer/frame_service_registry',
@@ skipping 659 matching lines @@
         function(err) {
           return toErrorRouteResponse_(err);
         });
   };
 
   /**
    * Terminates the route specified by |routeId|.
    * @param {!string} routeId
    */
   MediaRouteProvider.prototype.terminateRoute = function(routeId) {
-    this.handlers_.terminateRoute(routeId);
+    // TODO(crbug.com/627967): Remove code path that doesn't expect a Promise
+    // in M56

[apacible, 2016/07/14 16:46:36]

nitty nit: period at the end of this line.

[mark a. foltz, 2016/07/15 20:03:36]

Done.

+    var maybePromise = this.handlers_.terminateRoute(routeId);
+    var successResult = {result_code: RouteRequestResultCode.OK};
+    if (maybePromise) {
+      maybePromise.then(
+        function() { return successResult; },
+        function(err) { return toErrorRouteResponse_(err); });

[apacible, 2016/07/14 16:46:36]

Styling preference: move closing ");" to separate line.

...
  function(err) { return toErrorRouteResponse_(err); }
);

[mark a. foltz, 2016/07/15 20:03:36]

Done.

+    } else {
+      return successResult;
+    }
   };
 
   /**
    * Posts a message to the route designated by |routeId|.
    * @param {!string} routeId
    * @param {!string} message
    * @return {!Promise.<boolean>} Resolved with true if the message was sent,
    *    or false on failure.
    */
   MediaRouteProvider.prototype.sendRouteMessage = function(
@@ skipping 119 matching lines @@
   };
 
   mediaRouter = new MediaRouter(connector.bindHandleToProxy(
       serviceProvider.connectToService(
           mediaRouterMojom.MediaRouter.name),
       mediaRouterMojom.MediaRouter));
 
   return mediaRouter;
 });