[MD Bookmarks] Allow left/right keys to close/open folders in sidebar.

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 79 matching lines @@
       // Only the selected folder should be focusable.
       assertEquals('', 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').$.container.getAttribute('tabindex'));
+      assertEquals(
+          '0', getFolderNode('2').$.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.
       store.resetLastAction();
       keydown('7', 'ArrowDown');
       assertDeepEquals(null, store.lastAction);
 
       // Move up past closed folders.
       keydown('7', 'ArrowUp');
       assertDeepEquals(bookmarks.actions.selectFolder('2'), store.lastAction);
       assertFocused('7', '2');
 
       // Move up into parent.
       keydown('2', 'ArrowUp');
       assertDeepEquals(bookmarks.actions.selectFolder('1'), store.lastAction);
       assertFocused('2', '1');
 
       // Move up past start of list.
       store.resetLastAction();
       keydown('1', 'ArrowUp');
       assertDeepEquals(null, store.lastAction);
     });
+
+    test('keyboard left/right', function() {
+      store.data.closedFolders = new Set('2');
+      store.notifyObservers();
+
+      // Give keyboard focus to the first item.
+      getFolderNode('1').$.container.focus();
+
+      // Pressing right descends into first child.
+      keydown('1', 'ArrowRight');
+      assertDeepEquals(bookmarks.actions.selectFolder('2'), store.lastAction);
+
+      // Pressing right on a closed folder opens that folder
+      keydown('2', 'ArrowRight');
+      assertDeepEquals(
+          bookmarks.actions.changeFolderOpen('2', true), store.lastAction);
+
+      // Pressing right again descends into first child.
+      keydown('2', 'ArrowRight');
+      assertDeepEquals(bookmarks.actions.selectFolder('3'), store.lastAction);
+
+      // Pressing right on a folder with no children does nothing.
+      store.resetLastAction();
+      keydown('3', 'ArrowRight');
+      assertDeepEquals(null, store.lastAction);
+
+      // Pressing left on a folder with no children ascends to parent.
+      keydown('3', 'ArrowDown');
+      keydown('4', 'ArrowLeft');
+      assertDeepEquals(bookmarks.actions.selectFolder('2'), store.lastAction);
+
+      // Pressing left again closes the parent.
+      keydown('2', 'ArrowLeft');
+      assertDeepEquals(
+          bookmarks.actions.changeFolderOpen('2', false), store.lastAction);
+
+      // RTL flips left and right.
+      document.body.style.direction = 'rtl';

[tsergeant, 2017/05/09 04:43:42]

Nit: oh boy we'd better reset this after the test is done.

[calamity, 2017/05/11 04:09:30]

Done.

+      keydown('2', 'ArrowLeft');
+      assertDeepEquals(
+          bookmarks.actions.changeFolderOpen('2', true), store.lastAction);
+
+      keydown('2', 'ArrowRight');
+      assertDeepEquals(
+          bookmarks.actions.changeFolderOpen('2', false), store.lastAction);
+    });
   });
 
   mocha.run();
 });