[MD Bookmarks] Add keyboard navigation and selection to bookmark list.

chrome/test/data/webui/md_bookmarks/reducers_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.
 
 suite('selection state', function() {
   var selection;
   var action;
 
   function select(items, anchor, clear, toggle) {
     return {
@@ skipping 80 matching lines @@
 
   test('toggle an item', function() {
     action = select(['1', '2', '3'], '3', true, false);
     selection = bookmarks.SelectionState.updateSelection(selection, action);
 
     action = select(['1'], '3', false, true);
     selection = bookmarks.SelectionState.updateSelection(selection, action);
     assertDeepEquals(['2', '3'], normalizeSet(selection.items));
   });
 
+  test('update anchor', function() {
+    action = bookmarks.actions.updateAnchor('3');
+    selection = bookmarks.SelectionState.updateSelection(selection, action);
+
+    assertEquals('3', selection.anchor);
+  });
+
   test('deselects items when they are deleted', function() {
     var nodeMap = testTree(createFolder('0', [
       createFolder(
           '1',
           [
             createItem('2'),
             createItem('3'),
             createItem('4'),
           ]),
       createItem('5'),
@@ skipping 323 matching lines @@
     state = bookmarks.reduceAction(state, action);
 
     action = bookmarks.actions.removeBookmark('2', '1', 0, state.nodes);
     state = bookmarks.reduceAction(state, action);
 
     // 2 and 3 should be removed, since 2 was deleted and 3 was a descendant of
     // 2.
     assertDeepEquals(['1'], state.search.results);
   });
 });