Classes: Add support for stepping through default constructors

test/mjsunit/harmony/debug-step-into-constructor.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 --harmony-classes
+
+'use strict';
+
+var Debug = debug.Debug
+var done, stepCount;
+
+function listener(event, execState, eventData, data) {
+  if (event == Debug.DebugEvent.Break) {
+    if (!done) {
+      execState.prepareStep(Debug.StepAction.StepInto);
+      var s = execState.frame().sourceLineText();
+      print(s);
+      assertTrue(s.indexOf('// ' + stepCount + '.') !== -1);
+      stepCount++;
+    }
+  }
+};
+
+Debug.setListener(listener);
+
+
+class Base {
+  constructor() {
+    var x = 1;   // 1.
+    var y = 2;   // 2.
+    done = true; // 3.
+  }
+}
+
+class Derived extends Base {}
+
+
+(function TestBreakPointInConstructor() {
+  done = false;
+  stepCount = 1;
+  var bp = Debug.setBreakPoint(Base, 0);

[Dmitry Lomov (no reviews), 2014/11/14 17:19:15]

You can just use 'debugger;' in the places where you need a break point 

[arv (Not doing code reviews), 2014/11/14 17:24:00]

True. In this specific case, I wanted to make sure setting the break point
worked.

In the other cases I could change to use a debugger statement.

[Dmitry Lomov (no reviews), 2014/11/14 17:30:59]

Ah right, gotcha. I'll leave it up to you.

+
+  new Base();
+  assertEquals(4, stepCount);
+
+  Debug.clearBreakPoint(bp);
+})();
+
+
+(function TestDefaultConstructor() {
+  done = false;
+  stepCount = 1;
+
+  var bp = Debug.setBreakPoint(Base, 0);
+  new Derived();
+  assertEquals(4, stepCount);
+
+  Debug.clearBreakPoint(bp);
+})();
+
+
+(function TestStepInto() {
+  done = false;
+  stepCount = 0;
+
+  function f() {
+    new Derived();  // 0.
+  }
+
+  var bp = Debug.setBreakPoint(f, 0);
+  f();
+  assertEquals(4, stepCount);
+
+  Debug.clearBreakPoint(bp);
+})();
+
+
+(function TestExtraIndirection() {
+  done = false;
+  stepCount = 0;
+
+  class Derived2 extends Derived {}
+
+  function f() {
+    new Derived2();  // 0.
+  }
+
+  var bp = Debug.setBreakPoint(f, 0);
+  f();
+  assertEquals(4, stepCount);
+
+  Debug.clearBreakPoint(bp);
+})();
+
+
+(function TestBoundClass() {
+  done = false;
+  stepCount = 0;
+
+  var bound = Derived.bind(null);
+
+  function f() {
+    new bound();  // 0.
+  }
+
+  var bp = Debug.setBreakPoint(f, 0);
+  f();
+  assertEquals(4, stepCount);
+
+  Debug.clearBreakPoint(bp);
+})();
+
+
+Debug.setListener(null);