Remove unnecessary, left over Polymer.dom.flush() from appearance tests

chrome/test/data/webui/settings/appearance_page_test.js

Index: chrome/test/data/webui/settings/appearance_page_test.js
diff --git a/chrome/test/data/webui/settings/appearance_page_test.js b/chrome/test/data/webui/settings/appearance_page_test.js
index 4d62dbe9231a01ac16c418570bfcc6ac5ec86e83..4ade4fc2f9c366a241d3c4dff5e9d28d25dc3771 100644
--- a/chrome/test/data/webui/settings/appearance_page_test.js
+++ b/chrome/test/data/webui/settings/appearance_page_test.js
@@ -143,8 +143,6 @@ cr.define('settings_appearance', function() {
 
       if (cr.isLinux && !cr.isChromeOS) {
         test('useSystemTheme', function() {
-          Polymer.dom.flush();
-
           var button = appearancePage.$$('#useSystem');
           assertTrue(!!button);
           MockInteractions.tap(button);