fix(oauth2): addEventListener only if document state is not 'loading' (#7828)

Co-authored-by: Tim Lai <timothy.lai@gmail.com>

dev-helpers/oauth2-redirect.html

@@ -66,7 +66,11 @@
         window.close();
     }
 
-    window.addEventListener('DOMContentLoaded', function () {
+    if( document.readyState !== 'loading' ) {
       run();
-    });
+    } else {
+      document.addEventListener('DOMContentLoaded', function () {
+        run();
+      });
+    }
 </script>