WebUI: Update some more uses of the old-style i18ntemplate/LocalStrings.

ui/webui/resources/js/load_time_data.js

Index: ui/webui/resources/js/load_time_data.js
diff --git a/ui/webui/resources/js/load_time_data.js b/ui/webui/resources/js/load_time_data.js
index d7f99e161a251e3df8eabe38cc7f9f63cadf6d16..42f29fa43cad56795db93aebc81bf17c69f22e3b 100644
--- a/ui/webui/resources/js/load_time_data.js
+++ b/ui/webui/resources/js/load_time_data.js
@@ -23,6 +23,11 @@ function LoadTimeData() {}
   LoadTimeData.prototype = {
     /**
      * Sets the backing object.
+     *
+     * Note that there is no getter for |data_| to discourage abuse of the form:
+     *
+     *     var value = loadTimeData.data()['key'];
+     *
      * @param {Object} value The de-serialized page data.
      */
     set data(value) {
@@ -31,6 +36,14 @@ function LoadTimeData() {}
     },
 
     /**
+     * Returns a JsEvalContext for |data_|.
+     * @returns {JsEvalContext}
+     */
+    createJsEvalContext: function() {
+      return new JsEvalContext(this.data_);
+    },
+
+    /**
      * @param {string} id An ID of a value that might exist.
      * @return {boolean} True if |id| is a key in the dictionary.
      */