If shadow DOM is not supported, search for i18n attributes without using the /deep/ selector.

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 93 matching lines @@
               process(element, dictionary);
           }
         } else {
           element.setAttribute(propName, /** @type {string} */(value));
         }
       });
     }
   };
 
   var attributeNames = Object.keys(handlers);
-  var selector = 'html /deep/ [' + attributeNames.join('],[') + ']';
+  // Chrome for iOS must use Apple's UIWebView, which (as of April 2015) does
+  // 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('],[') + ']' :

[Dan Beam, 2015/06/23 23:33:12]

so this is whining in the console now about /deep/ being deprecated:

  /deep/ combinator is deprecated. See
https://www.chromestatus.com/features/6750456638341120 for more details.

+      '[' + attributeNames.join('],[') + ']';
 
   /**
    * Processes a DOM tree with the {@code dictionary} map.
    * @param {HTMLElement} node 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);
     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);
       }
     }
   }
 
   return {
     process: process
   };
 }());