MD Bookmarks: Lazily render dropdown menus

chrome/browser/resources/md_bookmarks/toolbar.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.
 
 Polymer({
   is: 'bookmarks-toolbar',
 
   behaviors: [
     bookmarks.StoreClient,
   ],
@@ skipping 60 matching lines @@
   get searchField() {
     return /** @type {CrToolbarElement} */ (this.$$('cr-toolbar'))
         .getSearchField();
   },
 
   /**
    * @param {Event} e
    * @private
    */
   onMenuButtonOpenTap_: function(e) {
-    var menu = /** @type {!CrActionMenuElement} */ (this.$.dropdown);
+    var menu = /** @type {!CrActionMenuElement} */ (this.$.dropdown.get());

[calamity, 2017/06/21 08:38:27]

Why does this not require an immediate flush?

[tsergeant, 2017/06/22 00:10:12]

The flush() is only needed to work with the dom-repeat, forcing the dom-repeat
to render its elements before the menu is positioned and shown.

Since this menu doesn't have a dom-repeat, all of its menu items will be
synchronously rendered during get().

     menu.showAt(/** @type {!Element} */ (e.target));
   },
 
   /** @private */
   onSortTap_: function() {
     chrome.bookmarkManagerPrivate.sortChildren(
         assert(this.getState().selectedFolder));
     bookmarks.ToastManager.getInstance().show(
         loadTimeData.getString('toastFolderSorted'), true);
     this.closeDropdownMenu_();
@@ skipping 35 matching lines @@
     commandManager.handle(Command.DELETE, selection);
   },
 
   /** @private */
   onClearSelectionTap_: function() {
     this.dispatch(bookmarks.actions.deselectItems());
   },
 
   /** @private */
   closeDropdownMenu_: function() {
-    var menu = /** @type {!CrActionMenuElement} */ (this.$.dropdown);
+    var menu = /** @type {!CrActionMenuElement} */ (this.$.dropdown.get());
     menu.close();
   },
 
   /**
    * @param {Event} e
    * @private
    */
   onSearchChanged_: function(e) {
     var searchTerm = /** @type {string} */ (e.detail);
     if (searchTerm != this.searchTerm_)
@@ skipping 34 matching lines @@
   },
 
   /**
    * @return {string}
    * @private
    */
   getItemsSelectedString_: function() {
     return loadTimeData.getStringF('itemsSelected', this.selectedItems_.size);
   },
 });