[MD settings] css for row separator

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 59ef458cef62f1a2a2469f31ff15a0587d3d3a61..bc3cb043002f6b400580fede4c6ca353331a0797 100644
--- a/chrome/test/data/webui/settings/appearance_page_test.js
+++ b/chrome/test/data/webui/settings/appearance_page_test.js
@@ -181,14 +181,14 @@ suite('AppearanceHandler', function() {
       assertFalse(!!appearancePage.$$('#useDefault'));
       assertFalse(!!appearancePage.$$('#useSystem'));
       // If there's no "USE" buttons, the container should be hidden.
-      assertTrue(appearancePage.$$('.secondary-action').hidden);
+      assertTrue(appearancePage.$$('#themesSecondaryActions').hidden);
 
       appearanceBrowserProxy.setIsSupervised(false);
       appearancePage.set(THEME_ID_PREF, 'fake theme id');
       Polymer.dom.flush();
       // If there's "USE" buttons again, the container should be visible.
       assertTrue(!!appearancePage.$$('#useDefault'));
-      assertFalse(appearancePage.$$('.secondary-action').hidden);
+      assertFalse(appearancePage.$$('#themesSecondaryActions').hidden);
 
       var button = appearancePage.$$('#useSystem');
       assertTrue(!!button);