[debugger] Further stepping support in test wrapper

test/mjsunit/debug-generator-break.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
-
-var Debug = debug.Debug;
-
-var break_count = 0;
-var exception = null;
-
-function listener(event, exec_state, event_data, data) {
-  if (event != Debug.DebugEvent.Break) return;
-  try {
-    break_count++;
-    var line = exec_state.frame(0).sourceLineText();
-    assertTrue(line.indexOf(`B${break_count}`) > 0);
-  } catch (e) {
-    exception = e;
-  }
-}
-
-Debug.setListener(listener);
-
-function* g() {
-  yield 1;
-}
-
-function* f() {
-  yield* g();                    // B1
-  assertEquals(2, break_count);  // B2
-  return 1;                      // B3
-}
-
-Debug.setBreakPoint(f, 1);
-Debug.setBreakPoint(f, 2);
-Debug.setBreakPoint(f, 3);
-
-for (let _ of f()) { }
-
-assertEquals(3, break_count);
-assertNull(exception);
-
-Debug.setListener(null);