new classes: special construct stub for derived classs and TDZ for `this`.

test/mjsunit/harmony/classes-experimental.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: --experimental-classes --harmony-classes
 
 'use strict';
 
 class Base {
-  constructor() {
+  constructor(a, b) {
     let o = new Object();
-    o.prp = 1;
+    o.prp = a + b;
     return o;
   }
 }
 
 class Subclass extends Base {
-  constructor() {
+  constructor(a, b) {
+    var exn;
     try {
       this.prp1 = 3;
     } catch (e) {
-      // TODO(dslomov): actually test the exception once TDZ is implemented.
+      exn = e;
     }
-    super();
-    assertSame(1, this.prp);
+    assertTrue(exn instanceof ReferenceError);
+    super(a, b);
+    assertSame(a + b, this.prp);
     assertSame(undefined, this.prp1);
     assertFalse(this.hasOwnProperty("prp1"));
     return this;
   }
 }
 
-let s = new Subclass();
+let b = new Base(1, 2);
+assertSame(3, b.prp);
+
+let s = new Subclass(2, -1);
 assertSame(1, s.prp);
 assertSame(undefined, s.prp1);
 assertFalse(s.hasOwnProperty("prp1"));