[Media Router WebUI] Run 'select cast mode' test in afterNextRender();

chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js

Index: chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js
diff --git a/chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js b/chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js
index b2b7336f39a83379089eb3404e50dcb859c383a8..d2c532416961945076711e2708ee857b4e4a2153 100644
--- a/chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js
+++ b/chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js
@@ -123,13 +123,12 @@ cr.define('media_router_container_cast_mode_list', function() {
       // Tests that |container| returns to SINK_LIST view and arrow drop icon
       // toggles after a cast mode is selected.
       test('select cast mode', function(done) {
-        setTimeout(function() {
+        Polymer.RenderStatus.afterNextRender(this, function() {
           container.castModeList = fakeCastModeListWithNonDefaultModesOnly;
 
           MockInteractions.tap(container.$['container-header'].
               $['arrow-drop-icon']);
           checkCurrentView(media_router.MediaRouterView.CAST_MODE_LIST);
-
           setTimeout(function() {
             var castModeList =
                 container.$$('#cast-mode-list').querySelectorAll('paper-item');