Remove --promise-extra flag

test/mjsunit/es6/debug-promises/reject-uncaught-uncaught.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // 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 --promise-extra
+// Flags: --expose-debug-as debug --allow-natives-syntax
 
 // Test debug events when we only listen to uncaught exceptions and
 // there is no catch handler for the to-be-rejected Promise.
 // We expect an Exception debug event with a promise to be triggered.
 
 Debug = debug.Debug;
 
 var expected_events = 1;
 var log = [];
 
 var p = new Promise(function(resolve, reject) {
   log.push("resolve");
   resolve();
 });
 
-var q = p.chain(
+var q = p.then(
   function() {
     log.push("reject");
     return Promise.reject(Error("uncaught reject"));  // event
   });
 
 function listener(event, exec_state, event_data, data) {
   try {
     if (event == Debug.DebugEvent.Exception) {
       expected_events--;
       assertTrue(expected_events >= 0);
@@ skipping 25 matching lines @@
       }
     } catch (e) {
       %AbortJS(e + "\n" + e.stack);
     }
   }
 
   %EnqueueMicrotask(checkResult);
 }
 
 testDone(0);