MD-Settings: A11y - Label drop down menus.

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

 <link rel="import" href="chrome://resources/html/md_select_css.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="../settings_shared_css.html">
 <link rel="import" href="../settings_vars_css.html">
 <link rel="import" href="constants.html">
 <link rel="import" href="site_settings_behavior.html">
 <link rel="import" href="site_settings_prefs_browser_proxy.html">
 
 <dom-module id="site-details-permission">
   <template>
     <style include="settings-shared md-select"></style>
     <div id="details" hidden>
       <div class="list-item underbar">
         <div>
           <iron-icon icon="[[icon]]">
           </iron-icon>
         </div>
         <div class="middle" id="permissionHeader">[[label]]</div>
         <div class="md-select-wrapper">
           <select id="permission" class="md-select"
+              aria-labelledby="permissionHeader"
               on-change="onPermissionSelectionChange_">
             <option id="allow" value$="[[PermissionValues.ALLOW]]">
               $i18n{siteSettingsActionAllow}
             </option>
             <option id="block" value$="[[PermissionValues.BLOCK]]">
               $i18n{siteSettingsActionBlock}
             </option>
             <option id="sessionOnly" value$="[[PermissionValues.SESSION_ONLY]]"
                 hidden$="[[!isCookiesCategory_(category)]]">
               $i18n{siteSettingsActionSessionOnly}
             </option>
           </select>
           <span class="md-select-underline"></span>
         </div>
       </div>
     </div>
   </template>
   <script src="site_details_permission.js"></script>
 </dom-module>