Add XMLHttpRequest method

src/polyfill/XMLHttpRequest.js

 
 const log = new Log('XMLHttpRequest')
 
-log.disable()
-// log.level(3)
+// log.disable()
+log.level(3)
 
 const UNSENT = 0
 const OPENED = 1
   }
 
   constructor() {
-    super()
     log.verbose('XMLHttpRequest constructor called')
+    super()
   }
 
 
     return this._responseType
   }
 
+  get isRNFBPolyfill() {
+    return true
+  }
+
 }