WebUI: fix cr-action-menu keyboard off-by-one issue

chrome/test/data/webui/cr_elements/cr_action_menu_test.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview Tests for cr-action-menu element. Runs as an interactive UI
  * test, since many of these tests check focus behavior.
  */
 suite('CrActionMenu', function() {
   /** @type {?CrActionMenuElement} */
@@ skipping 22 matching lines @@
 
   teardown(function() {
     if (menu.open)
       menu.close();
   });
 
   function down() {
     MockInteractions.keyDownOn(menu, 'ArrowDown', [], 'ArrowDown');
   }
 
+  function up() {
+    MockInteractions.keyDownOn(menu, 'ArrowUp', [], 'ArrowUp');
+  }
+
   test('hidden or disabled items', function() {
     menu.showAt(document.querySelector('#dots'));
     down();
     assertEquals(menu.root.activeElement, items[0]);
 
     menu.close();
     items[0].hidden = true;
     menu.showAt(document.querySelector('#dots'));
     down();
     assertEquals(menu.root.activeElement, items[1]);
 
     menu.close();
     items[1].disabled = true;
     menu.showAt(document.querySelector('#dots'));
     down();
     assertEquals(menu.root.activeElement, items[2]);
   });
 
   test('focus after down/up arrow', function() {
-    function up() {
-      MockInteractions.keyDownOn(menu, 'ArrowUp', [], 'ArrowUp');
-    }
-
     menu.showAt(document.querySelector('#dots'));
 
     // The menu should be focused when shown, but not on any of the items.
     assertEquals(menu, document.activeElement);
     assertNotEquals(items[0], menu.root.activeElement);
     assertNotEquals(items[1], menu.root.activeElement);
     assertNotEquals(items[2], menu.root.activeElement);
 
     down();
     assertEquals(items[0], menu.root.activeElement);
@@ skipping 10 matching lines @@
     up();
     assertEquals(items[0], menu.root.activeElement);
     up();
     assertEquals(items[2], menu.root.activeElement);
 
     items[1].disabled = true;
     up();
     assertEquals(items[0], menu.root.activeElement);
   });
 
+  test('pressing up arrow when no focus will focus last item', function(){
+    menu.showAt(document.querySelector('#dots'));
+    assertEquals(menu, document.activeElement);
+
+    up();
+    assertEquals(items[items.length - 1], menu.root.activeElement);
+  });
+
   test('close on resize', function() {
     menu.showAt(document.querySelector('#dots'));
     assertTrue(menu.open);
 
     window.dispatchEvent(new CustomEvent('resize'));
     assertFalse(menu.open);
   });
 
   test('close on popstate', function() {
     menu.showAt(document.querySelector('#dots'));
@@ skipping 41 matching lines @@
     assertEquals(menu, document.activeElement);
 
     // Mouse movements should override keyboard focus.
     down();
     down();
     assertEquals(items[1], menu.root.activeElement);
     makeMouseoverEvent(items[0]);
     assertEquals(items[0], menu.root.activeElement);
   });
 });