Introduce new stepping mode to step into another frame.

test/mjsunit/debug-stepframe.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
+
+function f0() {
+  var v00 = 0;              // Break 1
+  var v01 = 1;
+  // Normal function call in a catch scope.
+  try {
+    throw 1;
+  } catch (e) {
+    try{
+      f1();
+    } catch (e) {
+      var v02 = 2;          // Break 13
+    }
+  }
+  var v03 = 3;
+  var v04 = 4;
+}
+
+function f1() {
+  var v10 = 0;              // Break 2
+  var v11 = 1;
+  // Getter call.
+  var v12 = o.get;
+  var v13 = 3               // Break 4
+  // Setter call.
+  o.set = 2;
+  var v14 = 4;              // Break 6
+  // Function.prototype.call.
+  f2.call();
+  var v15 = 5;              // Break 12
+  var v16 = 6;
+  // Exit function by throw.
+  throw 1;
+  var v17 = 7;
+}
+
+function get() {
+  var g0 = 0;               // Break 3
+  var g1 = 1;
+  return 3;
+}
+
+function set() {
+  var s0 = 0;               // Break 5
+  return 3;
+}
+
+function f2() {
+  var v20 = 0;              // Break 7
+  // Construct call.
+  var v21 = new c0();
+  var v22 = 2;              // Break 9
+  // Bound function.
+  b0();
+  return 2;                 // Break 11
+}
+
+function c0() {
+  this.v0 = 0;              // Break 8
+  this.v1 = 1;
+}
+
+function f3() {
+  var v30 = 0;              // Break 10
+  var v31 = 1;
+  return 3;
+}
+
+var b0 = f3.bind(o);
+
+var o = {};
+Object.defineProperty(o, "get", { get : get });
+Object.defineProperty(o, "set", { set : set });
+
+Debug = debug.Debug;
+var break_count = 0
+var exception = null;
+var step_size;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    var line = exec_state.frame(0).sourceLineText();
+    print(line);
+    var match = line.match(/\/\/ Break (\d+)$/);
+    assertEquals(2, match.length);
+    assertEquals(break_count, parseInt(match[1]));
+    break_count += step_size;
+    exec_state.prepareStep(Debug.StepAction.StepFrame, step_size);
+  } catch (e) {
+    print(e + e.stack);
+    exception = e;
+  }
+}
+
+for (step_size = 1; step_size < 6; step_size++) {
+  print("step size = " + step_size);
+  break_count = 0;
+  Debug.setListener(listener);
+  debugger;                 // Break 0
+  f0();
+  Debug.setListener(null);  // Break 14
+  assertTrue(break_count > 14);
+}
+
+assertNull(exception);