[MD Bookmarks] Add a message to empty bookmark lists.

chrome/browser/resources/md_bookmarks/list.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/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/shadow.html">
 <link rel="import" href="chrome://bookmarks/item.html">
 <link rel="import" href="chrome://bookmarks/shared_style.html">
 
 <dom-module id="bookmarks-list">
   <template>
     <style include="shared-style">
       :host {
         padding: 20px 32px;
       }
 
       #bookmarks-card {
         @apply(--shadow-elevation-2dp);
         background-color: #fff;
         margin: 0 auto;
         max-width: var(--card-max-width);
         min-width: var(--card-min-width);
         padding: 8px 0;
       }
+
+      .centered-message {
+        align-items: center;
+        color: #6e6e6e;
+        display: flex;
+        font-size: 14px;
+        font-weight: 500;
+        height: 100%;
+        justify-content: center;
+      }
     </style>
     <dialog is="cr-action-menu" id="dropdown">
       <button class="dropdown-item" on-tap="onEditTap_">
         $i18n{menuEdit}
       </button>
       <button class="dropdown-item" on-tap="onCopyURLTap_">
         $i18n{menuCopyURL}
       </button>
       <button class="dropdown-item" on-tap="onDeleteTap_">
          $i18n{menuDelete}
       </button>
     </dialog>
-    <div id="bookmarks-card">
-      <!-- TODO(angelayang): handle empty folders -->
+    <div id="bookmarks-card"
+        hidden$="[[isListEmpty_(selectedNode.children.length)]]">
       <template is="dom-repeat" items="[[selectedNode.children]]" as="item">
         <bookmarks-item item="[[item]]"></bookmarks-item>
       </template>
     </div>
+    <div class="centered-message"
+        hidden$="[[!isListEmpty_(selectedNode.children.length)]]">
+      $i18n{emptyList}
+    </div>
   </template>
   <script src="chrome://bookmarks/list.js"></script>
 </dom-module>