[debugger] flood function for stepping on throw.

test/mjsunit/regress/regress-crbug-568477-3.js

+// Copyright 2015 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 expected = ["debugger;", "var x = y;", "debugger;", "var x = y;"];
+var log = [];
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    log.push(exec_state.frame(0).sourceLineText().trimLeft());
+    exec_state.prepareStep(Debug.StepAction.StepNext, 1);
+  } catch (e) {
+    %AbortJS(e + "\n" + e.stack);
+  }
+}
+
+Debug.setListener(listener);
+
+function f() {
+  var a = 1;
+  debugger;
+  var x = y;
+  print(x);
+}
+
+function call_f_with_deeper_stack() {
+  (() => () => () => f())()()();
+}
+
+var p = Promise.resolve();
+p.then(f);
+p.then(call_f_with_deeper_stack);
+
+// Schedule microtask to check against expectation at the end.
+function testDone(iteration) {
+  function checkResult() {
+    try {
+      assertTrue(iteration < 10);
+      if (expected.length == log.length) {
+        assertEquals(expected, log);
+      } else {
+        testDone(iteration + 1);
+      }
+    } catch (e) {
+      %AbortJS(e + "\n" + e.stack);
+    }
+  }
+
+  %EnqueueMicrotask(checkResult);
+}
+
+testDone(0);