[debugger] Migrate more debugger tests to inspector

test/debugger/debug/es6/debug-step-into-class-extends.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
 
 'use strict';
 
 var Debug = debug.Debug
 
 var done = false;
 var stepCount = 0;
 
 function listener(event, execState, eventData, data) {
   if (event == Debug.DebugEvent.Break) {
@@ skipping 17 matching lines @@
 
 function f() {
   class Derived extends GetBase() {} // 0.
 }
 
 var bp = Debug.setBreakPoint(f, 0);
 f();
 assertEquals(4, stepCount);
 
 Debug.setListener(null);