Update index.html (#708)

Author: zwu52

messaging/index.html

@@ -54,7 +54,7 @@ <h4>Registration Token</h4>
           <!-- div to display the UI to allow the request for permission to
                notify the user. This is shown if the app has not yet been
                granted permission to notify. -->
-          <div id="permission_div" style="display: none;">
+          <div id="permission_div" style="display: flex;">
             <h4>Needs Permission</h4>
             <p id="token"></p>
             <button class="mdl-button mdl-js-button mdl-button--raised mdl-button--colored"