MD Bookmarks: Show toolbar overlay when multiple items are selected

ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-media-query/iron-media-query.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_toolbar/cr_toolbar_search_field.html">
 
 <dom-module id="cr-toolbar">
   <template>
     <style>
       :host {
         --cr-toolbar-field-width: 580px;
@@ skipping 41 matching lines @@
       #centeredContent {
         display: flex;
         flex: 1 1 0;
         justify-content: center;
       }
 
       #rightContent {
         -webkit-margin-end: 12px;
       }
 
-      :host([narrow_]) #centeredContent {
+      :host([narrow]) #centeredContent {
         justify-content: flex-end;
       }
 
-      :host([narrow_][showing-search_]) #leftContent {
+      :host([narrow][showing-search_]) #leftContent {
         position: absolute;
         opacity: 0;
       }
 
-      :host(:not([narrow_])) #leftContent {
+      :host(:not([narrow])) #leftContent {
         flex: 1 1 var(--cr-toolbar-field-margin, 0);
       }
 
-      :host(:not([narrow_])) #rightContent {
+      :host(:not([narrow])) #rightContent {
         flex: 1 1 0;
         text-align: end;
       }
 
       #menuPromo {
         -webkit-padding-end: 12px;
         -webkit-padding-start: 8px;
         align-items: center;
         background: #616161;
         border-radius: 2px;
@@ skipping 55 matching lines @@
               <button id="closePromo" on-tap="onClosePromoTap_"
                   aria-label$="[[closeMenuPromo]]">&#x2715;</button>
             </paper-tooltip>
           </template>
         </template>
         <h1>[[pageName]]</h1>
       </div>
     </div>
 
     <div id="centeredContent">
-      <cr-toolbar-search-field id="search" narrow="[[narrow_]]"
+      <cr-toolbar-search-field id="search" narrow="[[narrow]]"
           label="[[searchPrompt]]" clear-label="[[clearLabel]]"
           spinner-active="[[spinnerActive]]"
           showing-search="{{showingSearch_}}">
       </cr-toolbar-search-field>
-      <iron-media-query query="(max-width: 900px)" query-matches="{{narrow_}}">
+      <iron-media-query query="(max-width: 900px)" query-matches="{{narrow}}">
       </iron-media-query>
     </div>
 
     <div id="rightContent">
       <content select=".more-actions"></content>
     </div>
   </template>
   <script src="cr_toolbar.js"></script>
 </dom-module>