MD Settings: Migrate omnibox extension action menu to settings-action-menu.

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

Index: chrome/test/data/webui/settings/search_engines_page_test.js
diff --git a/chrome/test/data/webui/settings/search_engines_page_test.js b/chrome/test/data/webui/settings/search_engines_page_test.js
index 76dd00b94917d16682a984e4c67e2e2c23075644..8933f98cb7d9fd0bbe52e57cf4892ca2a2db5f49 100644
--- a/chrome/test/data/webui/settings/search_engines_page_test.js
+++ b/chrome/test/data/webui/settings/search_engines_page_test.js
@@ -336,6 +336,9 @@ cr.define('settings_search_engines_page', function() {
         entry = document.createElement('settings-omnibox-extension-entry');
         entry.set('engine', createSampleOmniboxExtension());
         document.body.appendChild(entry);
+
+        // Open action menu.
+        MockInteractions.tap(entry.$$('paper-icon-button'));
       });
 
       teardown(function() { entry.remove(); });