Cleanup: Don't close single tags.

chrome/browser/resources/sync_internals/notifications.html

 <script src="chrome://sync-internals/notifications.js"></script>
 
 <style>
 table#notificationInfo tr:nth-child(odd) {
   background: #eff3ff;
 }
 </style>
 
 <p id='notificationStateInfo'>
   State: <span jscontent='notificationState'></span>
 </p>
 <table id='notificationInfo'>
   <tr>
     <th>Type</th>
     <th>Total count</th>
     <th>Session count</th>
     <th>Payload</th>
   </tr>
   <tr jsselect='notifications'>
-    <td jscontent='type'/>
-    <td jscontent='totalCount'/>
-    <td jscontent='sessionCount'/>
-    <td jscontent='payload'/>
+    <td jscontent='type'></td>
+    <td jscontent='totalCount'></td>
+    <td jscontent='sessionCount'></td>
+    <td jscontent='payload'></td>
   </tr>
 </table>