[es6] Perform the IsConstructor test in GetSuperConstructor.

test/webkit/class-syntax-extends.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 // 1.  Redistributions of source code must retain the above copyright
 //     notice, this list of conditions and the following disclaimer.
 // 2.  Redistributions in binary form must reproduce the above copyright
 //     notice, this list of conditions and the following disclaimer in the
@@ skipping 80 matching lines @@
 shouldBe('x = 1; namespace = {}; namespace.A = class { constructor() { } }; try { namespace.B = class extends (namespace.A, x++) { constructor() { } } } catch (e) { } x', '2');
 
 shouldBe('Object.getPrototypeOf((class { constructor () { } }).prototype)', 'Object.prototype');
 shouldBe('Object.getPrototypeOf((class extends null { constructor () { super(); } }).prototype)', 'null');
 shouldThrow('new (class extends undefined { constructor () { this } })', '"TypeError: Class extends value undefined is not a constructor or null"');
 shouldThrow('new (class extends undefined { constructor () { super(); } })', '"TypeError: Class extends value undefined is not a constructor or null"');
 shouldThrow('x = {}; new (class extends undefined { constructor () { return x; } })', '"TypeError: Class extends value undefined is not a constructor or null"');
 shouldThrow('y = 12; new (class extends undefined { constructor () { return y; } })', '"TypeError: Class extends value undefined is not a constructor or null"');
 shouldBeTrue ('class x {}; new (class extends null { constructor () { return new x; } }) instanceof x');
 shouldThrow('new (class extends null { constructor () { this; } })', '"ReferenceError: this is not defined"');
-shouldThrow('new (class extends null { constructor () { super(); } })', '"TypeError: super is not a constructor"');
+shouldThrow('new (class extends null { constructor () { super(); } })', '"TypeError: Super constructor null of anonymous class is not a constructor"');
 shouldBe('x = {}; new (class extends null { constructor () { return x } })', 'x');
 shouldThrow('y = 12; new (class extends null { constructor () { return y; } })', '"TypeError: Derived constructors may only return object or undefined"');
 shouldBeTrue ('class x {}; new (class extends null { constructor () { return new x; } }) instanceof x');
 shouldBe('x = null; Object.getPrototypeOf((class extends x { }).prototype)', 'null');
 shouldBeTrue('Object.prototype.isPrototypeOf(class { })');
 shouldBeTrue('Function.prototype.isPrototypeOf(class { })');
 
 var successfullyParsed = true;