[MD Bookmarks] Modify search to retain the previously selected folder.

chrome/test/data/webui/md_bookmarks/sidebar_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.
 
 suite('<bookmarks-sidebar>', function() {
   var sidebar;
   var TEST_TREE;
 
   setup(function() {
     TEST_TREE = createFolder('0', [
@@ skipping 13 matching lines @@
       createFolder('8', []),
     ]);
 
     setupTreeForUITests(TEST_TREE);
     sidebar = document.createElement('bookmarks-sidebar');
     replaceBody(sidebar);
     sidebar.rootFolders = TEST_TREE.children;
   });
 
   test('selecting and deselecting folders fires event', function() {
-    var firedId;
+    var firedId, clearSearch;
     document.addEventListener('selected-folder-changed', function(e) {
-      firedId = /** @type {string} */ (e.detail);
+      firedId = /** @type {string} */ (e.detail.id);
+      clearSearch = /** @type {string} */ (e.detail.clearSearch);
     });
 
     Polymer.dom.flush();
     var rootFolders = sidebar.$['folder-tree'].children;
     var firstGen = rootFolders[0].$['descendants'].querySelectorAll(
         'bookmarks-folder-node');
     var secondGen =
         firstGen[0].$['descendants'].querySelectorAll('bookmarks-folder-node');
 
     // Select nested folder.
     firedId = '';
     MockInteractions.tap(secondGen[0].$['folder-label']);
     assertEquals(secondGen[0].item.id, firedId);
+    assertTrue(clearSearch);
 
     // Select folder in a separate subtree.
     firedId = '';
     MockInteractions.tap(rootFolders[1].$['folder-label']);
     assertEquals(rootFolders[1].item.id, firedId);
   });
 });