[debugger] Further stepping support in test wrapper

test/debugger/debugger/debug-step.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.
-
-Debug = new DebugWrapper();
-Debug.enable();
-
-// Simple debug event handler which performs 100 steps and then retrieves
-// the resulting value of "i" in f().
-
-function listener(event, exec_state, event_data, data) {
-  if (event == Debug.DebugEvent.Break) {
-    if (step_count > 0) {
-      Debug.stepInto();
-      step_count--;
-    } else {
-      const frameid = exec_state.frames[0].callFrameId;
-      result = Debug.evaluate(frameid, "i").value;
-    }
-  }
-};
-
-// Add the debug event listener.
-Debug.setListener(listener);
-
-// Test debug event for break point.
-function f() {
-  var i;                       // Line 1.
-  for (i = 0; i < 100; i++) {  // Line 2.
-    x = 1;                     // Line 3.
-  }
-};
-
-// Set a breakpoint on the for statement (line 1).
-Debug.setBreakPoint(f, 1);
-
-// Check that performing 100 steps will make i 33.
-let step_count = 100;
-let result = -1;
-
-f();
-
-assertEquals(33, result);