MD User Manager: fixes accessibility issues

chrome/browser/resources/md_user_manager/supervised_user_create_confirm.html

 <link rel="import" href="chrome://md-user-manager/profile_browser_proxy.html">
 <link rel="import" href="chrome://md-user-manager/shared_styles.html">
 <link rel="import" href="chrome://resources/html/parse_html_subset.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/util.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icons/iron-icons.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 
 <dom-module id="supervised-user-create-confirm">
@@ skipping 58 matching lines @@
     <div id="container">
       <div id="title-area" class="horizontal justified layout">
         <span id="title">[[titleText_(profileInfo)]]</span>
         <iron-icon icon="supervisor-account"></iron-icon>
       </div>
       <div class="content-area">
         <div class="content" inner-h-t-m-l="[[htmlMessage1_(profileInfo)]]">
         </div>
         <div id="childlock-button-example">
           <iron-icon icon="lock"></iron-icon>
-          <span i18n-content="exitAndChildlockLabel"></span>
+          <span>$i18n{exitAndChildlockLabel}</span>
         </div>
         <div class="content" inner-h-t-m-l="[[htmlMessage2_(profileInfo)]]">
         </div>
       </div>
       <div id="actions">
-        <paper-button id="ok" class="action secondary" on-tap="onOkTap_"
-            i18n-content="supervisedUserCreatedDone">
+        <paper-button id="ok" class="action secondary" on-tap="onOkTap_">
+          $i18n{supervisedUserCreatedDone}
         </paper-button>
         <paper-button id="switchUser" class="action primary"
             on-tap="onSwitchUserTap_">
           [[switchUserText_(profileInfo)]]
         </paper-button>
       </div>
     </div>
   </template>
   <script src="chrome://md-user-manager/supervised_user_create_confirm.js"></script>
 </dom-module>