Disable non-standard Promise functions in staging

test/mjsunit/es6/debug-promises/throw-with-undefined-reject.js

Index: test/mjsunit/es6/debug-promises/throw-with-undefined-reject.js
diff --git a/test/mjsunit/es6/debug-promises/throw-with-undefined-reject.js b/test/mjsunit/es6/debug-promises/throw-with-undefined-reject.js
index c88feb9c397080974240980ca4ae5dfd853d951d..7fa60f86cf05c4fda779d4a9b22b185b76a1217b 100644
--- a/test/mjsunit/es6/debug-promises/throw-with-undefined-reject.js
+++ b/test/mjsunit/es6/debug-promises/throw-with-undefined-reject.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --expose-debug-as debug --allow-natives-syntax
+// Flags: --expose-debug-as debug --allow-natives-syntax --promise-extra
 
 // Test debug events when an exception is thrown inside a Promise, which is
 // caught by a custom promise, which has no reject handler.