MD Settings: Use <button class="dropdown-item"> for drop-down options.

chrome/browser/resources/settings/site_settings/site_data_details_dialog.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-dropdown-menu/paper-dropdown-menu.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-item.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-listbox/paper-listbox.html">
 <link rel="import" href="/i18n_setup.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="site-data-details-dialog">
   <template>
     <style include="settings-shared">
       .remove-button {
         margin-top: 12px;
       }
     </style>
     <cr-dialog id="dialog">
       <div class="title">
         [[title_]]
       </div>
       <div class="body">
         <div class="layout horizontal" id="container">
           <div class="flex">
             <paper-dropdown-menu>
               <paper-listbox id="picker" class="dropdown-content"
                   attr-for-selected="picker-value"
                   on-iron-activate="onItemSelected_">
                 <template is="dom-repeat" items="[[entries_]]">
-                  <paper-item picker-value$="[[item.id]]">
+                  <button class="dropdown-item" role="option"
+                      picker-value$="[[item.id]]">
                     [[item.title]]
-                  </paper-item>
+                  </button>
                 </template>
               </paper-listbox>
             </paper-dropdown-menu>
           </div>
           <div class="button-container">
             <paper-button on-tap="onRemove_"
                 class="cancel-button remove-button">
               $i18n{siteSettingsCookieRemove}
             </paper-button>
           </div>
@@ skipping 10 matching lines @@
             $i18n{siteSettingsCookieRemoveAll}
           </paper-button>
         </div>
       </div>
     </cr-dialog>
   </template>
   <script src="cookie_info.js"></script>
   <script src="cookie_tree_node.js"></script>
   <script src="site_data_details_dialog.js"></script>
 </dom-module>