MD Bookmarks: Focus sidebar nodes on click without showing an outline

chrome/test/data/webui/md_bookmarks/md_bookmarks_focus_test.js

 // Copyright 2017 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 MD Bookmarks which are run as interactive ui tests.
  * Should be used for tests which care about focus.
  */
 
 var ROOT_PATH = '../../../../../';
@@ skipping 54 matching lines @@
       rootNode = document.createElement('bookmarks-folder-node');
       rootNode.itemId = '0';
       rootNode.depth = -1;
       replaceBody(rootNode);
       Polymer.dom.flush();
     });
 
     test('keyboard selection', function() {
       function assertFocused(oldFocus, newFocus) {
         assertEquals(
-            '', getFolderNode(oldFocus).$.container.getAttribute('tabindex'));
+            '-1', getFolderNode(oldFocus).$.container.getAttribute('tabindex'));
         assertEquals(
             '0', getFolderNode(newFocus).$.container.getAttribute('tabindex'));
         assertEquals(
             getFolderNode(newFocus).$.container,
             getFolderNode(newFocus).root.activeElement);
       }
 
       store.data.closedFolders = new Set('2');
       store.notifyObservers();
 
       // The selected folder is focus enabled on attach.
       assertEquals(
           '0', getFolderNode('1').$.container.getAttribute('tabindex'));
 
-      // Only the selected folder should be focusable.
-      assertEquals('', getFolderNode('2').$.container.getAttribute('tabindex'));
+      // Only the selected folder should be keyboard focusable.
+      assertEquals(
+          '-1', getFolderNode('2').$.container.getAttribute('tabindex'));
 
       // Give keyboard focus to the first item.
       getFolderNode('1').$.container.focus();
 
       // Move down into child.
       keydown('1', 'ArrowDown');
 
       assertDeepEquals(bookmarks.actions.selectFolder('2'), store.lastAction);
       store.data.selectedFolder = '2';
       store.notifyObservers();
 
-      assertEquals('', getFolderNode('1').$.container.getAttribute('tabindex'));
+      assertEquals(
+          '-1', getFolderNode('1').$.container.getAttribute('tabindex'));
       assertEquals(
           '0', getFolderNode('2').$.container.getAttribute('tabindex'));
       assertFocused('1', '2');
 
       // Move down past closed folders.
       keydown('2', 'ArrowDown');
       assertDeepEquals(bookmarks.actions.selectFolder('7'), store.lastAction);
       assertFocused('2', '7');
 
       // Move down past end of list.
@@ skipping 227 matching lines @@
 
       keydown(focusedItem, 'ArrowDown', ['ctrl', 'shift']);
       focusedItem = items[3];
       assertDeepEquals(
           ['2', '4', '5', '6'], normalizeSet(store.data.selection.items));
     });
   });
 
   mocha.run();
 });