[MD Bookmarks] Prevent sorting of empty folders.

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 26 matching lines @@
     /** @private {!Set<string>} */
     selectedItems_: Object,
 
     /** @private */
     globalCanEdit_: Boolean,
 
     /** @private */
     selectedFolder_: String,
 
     /** @private */
+    canSortFolder_: {
+      type: Boolean,
+      computed: 'computeCanSortFolder_(canChangeList_, selectedFolder_)',
+    },
+
+    /** @private */
     canChangeList_: {
       type: Boolean,
       computed:
           'computeCanChangeList_(selectedFolder_, searchTerm_, globalCanEdit_)',
     }
   },
 
   attached: function() {
     this.watch('searchTerm_', function(state) {
       return state.search.term;
@@ skipping 20 matching lines @@
    * @param {Event} e
    * @private
    */
   onMenuButtonOpenTap_: function(e) {
     var menu = /** @type {!CrActionMenuElement} */ (this.$.dropdown.get());
     menu.showAt(/** @type {!Element} */ (e.target));
   },
 
   /** @private */
   onSortTap_: function() {
-    chrome.bookmarkManagerPrivate.sortChildren(
-        assert(this.getState().selectedFolder));
+    chrome.bookmarkManagerPrivate.sortChildren(assert(this.selectedFolder_));
     bookmarks.ToastManager.getInstance().show(
         loadTimeData.getString('toastFolderSorted'), true);
     this.closeDropdownMenu_();
   },
 
   /** @private */
   onAddBookmarkTap_: function() {
     var dialog =
         /** @type {BookmarksEditDialogElement} */ (this.$.addDialog.get());
-    dialog.showAddDialog(false, assert(this.getState().selectedFolder));
+    dialog.showAddDialog(false, assert(this.selectedFolder_));
     this.closeDropdownMenu_();
   },
 
   /** @private */
   onAddFolderTap_: function() {
     var dialog =
         /** @type {BookmarksEditDialogElement} */ (this.$.addDialog.get());
-    dialog.showAddDialog(true, assert(this.getState().selectedFolder));
+    dialog.showAddDialog(true, assert(this.selectedFolder_));
     this.closeDropdownMenu_();
   },
 
   /** @private */
   onImportTap_: function() {
     chrome.bookmarks.import();
     this.closeDropdownMenu_();
   },
 
   /** @private */
   onExportTap_: function() {
     chrome.bookmarks.export();
     this.closeDropdownMenu_();
   },
 
   /** @private */
   onDeleteSelectionTap_: function() {
-    var selection = this.getState().selection.items;
+    var selection = this.selectedItems_;
     var commandManager = bookmarks.CommandManager.getInstance();
     assert(commandManager.canExecute(Command.DELETE, selection));
     commandManager.handle(Command.DELETE, selection);
   },
 
   /** @private */
   onClearSelectionTap_: function() {
     this.dispatch(bookmarks.actions.deselectItems());
   },
 
@@ skipping 19 matching lines @@
   },
 
   /** @private */
   onSearchTermChanged_: function() {
     this.searchField.setValue(this.searchTerm_ || '');
   },
 
   /**
    * @return {boolean}
    * @private
+   */
+  computeCanSortFolder_: function() {
+    return this.canChangeList_ &&
+        this.getState().nodes[this.selectedFolder_].children.length > 0;
+  },
+
+  /**
+   * @return {boolean}
+   * @private
    */
   computeCanChangeList_: function() {
     return !this.searchTerm_ &&
         bookmarks.util.canReorderChildren(
             this.getState(), this.selectedFolder_);
   },
 
   /**
    * @return {boolean}
    * @private
    */
   shouldShowSelectionOverlay_: function() {
     return this.selectedItems_.size > 1 && this.globalCanEdit_;
   },
 
   canDeleteSelection_: function() {
     return bookmarks.CommandManager.getInstance().canExecute(
         Command.DELETE, this.selectedItems_);
   },
 
   /**
    * @return {string}
    * @private
    */
   getItemsSelectedString_: function() {
     return loadTimeData.getStringF('itemsSelected', this.selectedItems_.size);
   },
 });