[MD Bookmarks] Prevent sorting of empty folders.

chrome/browser/resources/md_bookmarks/toolbar.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 
 <link rel="import" href="chrome://resources/cr_elements/cr_action_menu/cr_action_menu.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_lazy_render/cr_lazy_render.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_toolbar/cr_toolbar.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_toolbar/cr_toolbar_selection_overlay.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://bookmarks/edit_dialog.html">
 <link rel="import" href="chrome://bookmarks/shared_style.html">
 <link rel="stylesheet" href="chrome://resources/css/md_colors.css">
@@ skipping 46 matching lines @@
           class="more-actions more-vert-button"
           title="$i18n{organizeButtonTitle}"
           on-tap="onMenuButtonOpenTap_">
         <div></div>
         <div></div>
         <div></div>
       </button>
     </cr-toolbar>
     <template is="cr-lazy-render" id="dropdown">
       <dialog is="cr-action-menu" role="menu">
-        <button class="dropdown-item"
+        <button id="sortButton"
+            class="dropdown-item"
             on-tap="onSortTap_"
-            disabled="[[!canChangeList_]]"
+            disabled="[[!canSortFolder_]]"
             role="menuitem">
           $i18n{menuSort}
         </button>
         <hr>
         <button id="addBookmarkButton"
             class="dropdown-item"
             on-tap="onAddBookmarkTap_"
             disabled="[[!canChangeList_]]"
             role="menuitem">
           $i18n{menuAddBookmark}
@@ skipping 27 matching lines @@
           cancel-label="$i18n{cancel}"
           selection-label="[[getItemsSelectedString_(selectedItems_.size)]]"
           delete-disabled="[[!canDeleteSelection_(selectedItems_)]]"
           on-delete-selected-items="onDeleteSelectionTap_"
           on-clear-selected-items="onClearSelectionTap_">
       </cr-toolbar-selection-overlay>
     </template>
   </template>
   <script src="chrome://bookmarks/toolbar.js"></script>
 </dom-module>