MD Settings: Migrate startup URL action menu to settings-action-menu.

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

Index: chrome/test/data/webui/settings/startup_urls_page_test.js
diff --git a/chrome/test/data/webui/settings/startup_urls_page_test.js b/chrome/test/data/webui/settings/startup_urls_page_test.js
index f8dd9cda179471f5dd3ba86c39a8d7e805323c31..ce0aeea1500dd7ce8cbf0ea52686acf72985798c 100644
--- a/chrome/test/data/webui/settings/startup_urls_page_test.js
+++ b/chrome/test/data/webui/settings/startup_urls_page_test.js
@@ -256,10 +256,10 @@ cr.define('settings_startup_urls_page', function() {
       document.body.appendChild(element);
 
       // Bring up the popup menu for the following tests to use.
-      assertFalse(!!element.$$('iron-dropdown'));
+      assertFalse(!!element.$$('dialog[is=settings-action-menu]'));
       MockInteractions.tap(element.$.dots);
       Polymer.dom.flush();
-      assertTrue(!!element.$$('iron-dropdown'));
+      assertTrue(!!element.$$('dialog[is=settings-action-menu]'));
     });
 
     teardown(function() { element.remove(); });