[debugger] Further stepping support in test wrapper

test/debugger/debug/debug-stepin-accessor-ic.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
 
 function get() {
   return 3;                       // Break
 }                                 // Break
 
 function set(x) {
   this.x = x;                     // Break
 }                                 // Break
 
 var o = {};
@@ skipping 24 matching lines @@
 
 var Debug = debug.Debug;
 Debug.setListener(listener);
 
 debugger;                         // Break
 f();                              // Break
 
 Debug.setListener(null);          // Break
 assertEquals(86, break_count);
 assertNull(exception);