[debugger] Further stepping support in test wrapper

test/mjsunit/debug-stack-check-position.js

-// Copyright 2016 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
-
-var Debug = debug.Debug;
-var exception = null;
-var loop = true;
-
-function listener(event, exec_state, event_data, data) {
-  if (event != Debug.DebugEvent.Break) return;
-  try {
-    assertTrue(exec_state.frame(0).sourceLineText().indexOf("BREAK") > 0);
-  } catch (e) {
-    exception = e;
-  }
-}
-
-function f() {     // BREAK
-  return 1;
-}
-
-Debug.setListener(listener);
-
-%ScheduleBreak();  // Break on function entry.
-f();
-
-Debug.setListener(null);
-assertNull(exception);