MD Bookmarks: Implement 'Sort by Title' menu button

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/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">
 
 <dom-module id="bookmarks-toolbar">
   <template>
     <style include="shared-style">
       button.more-actions {
         margin: 4px;
       }
 
       button.more-vert-button div {
         border-color: white;
       }
 
       cr-toolbar {
         --cr-toolbar-field-margin:
             calc(var(--sidebar-width) + var(--splitter-width));
         background: var(--md-toolbar-color);
       }
     </style>
     <dialog is="cr-action-menu" id="dropdown">
-      <button class="dropdown-item" on-tap="onSortTap_">
+      <button class="dropdown-item" on-tap="onSortTap_"
+          disabled="[[hasSearchTerm_(searchTerm_)]]">
         $i18n{menuSort}
       </button>
       <hr>
       <button class="dropdown-item" on-tap="onAddBookmarkTap_"
           disabled="[[hasSearchTerm_(searchTerm_)]]">
         $i18n{menuAddBookmark}
       </button>
       <button class="dropdown-item" on-tap="onAddFolderTap_"
           disabled="[[hasSearchTerm_(searchTerm_)]]">
         $i18n{menuAddFolder}
@@ skipping 16 matching lines @@
         <div></div>
         <div></div>
       </button>
     </cr-toolbar>
     <template is="cr-lazy-render" id="addDialog">
       <bookmarks-edit-dialog></bookmarks-edit-dialog>
     </template>
   </template>
   <script src="chrome://bookmarks/toolbar.js"></script>
 </dom-module>