Minimize flicker by adding a   to nodes that will have

ui/webui/resources/js/i18n_template_no_process.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview This is a simple template engine inspired by JsTemplates
  * optimized for i18n.
  *
  * It currently supports three handlers:
  *
@@ skipping 104 matching lines @@
   // not have native shadow DOM support. If shadow DOM is supported (or
   // polyfilled), search for i18n attributes using the /deep/ selector;
   // otherwise, do not attempt to search within the shadow DOM.
   var selector =
       (window.document.body && window.document.body.createShadowRoot) ?
       'html /deep/ [' + attributeNames.join('],[') + ']' :
       '[' + attributeNames.join('],[') + ']';
 
   /**
    * Processes a DOM tree with the {@code dictionary} map.
-   * @param {HTMLElement} node The root of the DOM tree to process.
+   * @param {Document|Element} root The root of the DOM tree to process.
    * @param {LoadTimeData} dictionary The dictionary to draw from.
    */
-  function process(node, dictionary) {
-    var elements = node.querySelectorAll(selector);
+  function process(root, dictionary) {
+    var elements = root.querySelectorAll(selector);
     for (var element, i = 0; element = elements[i]; i++) {
       for (var j = 0; j < attributeNames.length; j++) {
         var name = attributeNames[j];
         var attribute = element.getAttribute(name);
         if (attribute != null)
           handlers[name](element, attribute, dictionary);
       }
     }
+    var doc = root instanceof Document ? root : root.ownerDocument;
+    if (doc)
+      doc.documentElement.classList.add('i18n-processed');
   }
 
   return {
     process: process
   };
 }());