more polyfill for IE

www/common/sframe-boot2.js

@@ -18,6 +18,14 @@ define([
         Number.MAX_SAFE_INTEGER = 9007199254740991;
     }
 
+    if (typeof(window.Symbol) !== 'function') {
+        var idCounter = 0;
+        var Symbol = window.Symbol = function Symbol(key) {
+            return '__' + key + '_' + Math.floor(Math.random() * 1e9) + '_' + (++idCounter) + '__';
+        };
+        Symbol.iterator = Symbol('Symbol.iterator');
+    }
+
     var mkFakeStore = function () {
         var fakeStorage = {
             getItem: function (k) { return fakeStorage[k]; },