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

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

Index: chrome/test/data/webui/cr_elements/cr_action_menu_test.js
diff --git a/chrome/test/data/webui/cr_elements/cr_action_menu_test.js b/chrome/test/data/webui/cr_elements/cr_action_menu_test.js
index 254336070c26f9198296d3127c8c629791417e4e..6b9a375a2bb0812d87a4e6d9cdd78d9ea2c6b6f2 100644
--- a/chrome/test/data/webui/cr_elements/cr_action_menu_test.js
+++ b/chrome/test/data/webui/cr_elements/cr_action_menu_test.js
@@ -40,6 +40,10 @@ suite('CrActionMenu', function() {
     MockInteractions.keyDownOn(menu, 'ArrowDown', [], 'ArrowDown');
   }
 
+  function up() {
+    MockInteractions.keyDownOn(menu, 'ArrowUp', [], 'ArrowUp');
+  }
+
   test('hidden or disabled items', function() {
     menu.showAt(document.querySelector('#dots'));
     down();
@@ -59,10 +63,6 @@ suite('CrActionMenu', function() {
   });
 
   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.
@@ -93,6 +93,13 @@ suite('CrActionMenu', function() {
     assertEquals(items[0], menu.root.activeElement);
   });
 
+  test('pressing up arrow when no focus will focus last item', function(){
+    menu.showAt(document.querySelector('#dots'));

[dpapad, 2017/04/05 21:49:13]

assertEquals(menu, document.activeElement);

[scottchen, 2017/04/06 17:54:02]

Done.

+
+    up();
+    assertEquals(items[2], menu.root.activeElement);

[dpapad, 2017/04/05 21:49:13]

Nit (optional): Make it more explicit that we expect the last item to be
focused.

assertEquals(items[items.length - 1], menu.root.activeElement);

[scottchen, 2017/04/06 17:54:02]

Done.

+  });
+
   test('close on resize', function() {
     menu.showAt(document.querySelector('#dots'));
     assertTrue(menu.open);