First attempt at creating a first-run page

i18n.js

 /*
  * This Source Code is subject to the terms of the Mozilla Public License
  * version 2.0 (the "License"). You can obtain a copy of the License at
  * http://mozilla.org/MPL/2.0/.
  */
 
 // Loads and inserts i18n strings into matching elements. Any inner HTML already in the
 // element is parsed as JSON and used as parameters to substitute into placeholders in the
 // i18n message.
 function loadI18nStrings() {
   var nodes = document.querySelectorAll("[class^='i18n_']");
   for(var i = 0; i < nodes.length; i++) {
     var arguments = JSON.parse("[" + nodes[i].textContent + "]");
-    var stringName = nodes[i].className.split(/\s/)[0].substring(5);
+    var className = nodes[i].className;
+    if (className instanceof SVGAnimatedString)
+      className = className.animVal;
+    var stringName = className.split(/\s/)[0].substring(5);
+    var prop = "innerHTML" in nodes[i] ? "innerHTML" : "textContent";
     if(arguments.length > 0)
-      nodes[i].innerHTML = chrome.i18n.getMessage(stringName, arguments);
+      nodes[i][prop] = chrome.i18n.getMessage(stringName, arguments);
     else
-      nodes[i].innerHTML = chrome.i18n.getMessage(stringName);
+      nodes[i][prop] = chrome.i18n.getMessage(stringName);
   }
 }
 
 function i18n_time(h, m) {
   var locale = chrome.i18n.getMessage("@@ui_locale");
   if(m < 10)
     m = "0" + m;
   if(locale == "fr") {
     return h + "h" + m;
   } else {
@@ skipping 12 matching lines @@
 function i18n_timeDateStrings(when) {
   var d = new Date(when);
   var timeString = d.toLocaleTimeString();
 
   var now = new Date();
   if (d.toDateString() == now.toDateString())
     return [timeString];
   else
     return [timeString, d.toLocaleDateString()];
 }
+
+// Fill in the strings as soon as possible
+window.addEventListener("DOMContentLoaded", loadI18nStrings, true);