Revert "Detect if DOMException exists via typeof instead of trying to call it...

Revert "Detect if DOMException exists via typeof instead of trying to call it and catching the exception which may get thrown"

This reverts commit e3298525.

fetch.js

@@ -462,8 +462,9 @@ Response.redirect = function(url, status) {
 }
 
 export var DOMException = global.DOMException
-
-if (typeof DOMException !== 'function') {
+try {
+  new DOMException()
+} catch (err) {
   DOMException = function(message, name) {
     this.message = message
     this.name = name