Copy new JS Interop test from dev_compiler test suite.

tests/html/js_typed_interop_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 @JS()
 library js_typed_interop_test;
 
 import 'dart:html';
 
 import 'package:js/js.dart';
@@ skipping 62 matching lines @@
 
   function _PrivateClass(a, b) {
     this._a = a;
     this._b = b;
   };
 
   _PrivateClass.prototype = {
     _getA: function() { return this._a;}
   };
 
-  var selection = ["a", "b", "c", foo, bar];  
+  var selection = ["a", "b", "c", foo, bar];
 
   function returnNumArgs() { return arguments.length; };
   function returnLastArg() { return arguments[arguments.length-1]; };
 
   function confuse(obj) { return obj; }
 
   window['class'] = function() { return 42; };
   window['delete'] = 100;
   window['JS$hasJsInName'] = 'unicorn';
   window['JS$hasJsInNameMethod'] = function(x) { return x*5; };
@@ skipping 43 matching lines @@
 }
 
 @JS('ClassWithConstructor')
 class _ClassWithConstructor {
   external _ClassWithConstructor(aParam, bParam);
   external getA();
   external get a;
   external get b;
 }
 
+@JS('ClassWithConstructor')
+class ClassWithFactory {
+  external factory ClassWithFactory(aParam, bParam);
+  external getA();
+  external get a;
+  external get b;
+}
+
 @JS()
 class JS$_PrivateClass {
   external JS$_PrivateClass(aParam, bParam);
   external JS$_getA();
   external get JS$_a;
   external get JS$_b;
   // Equivalent to JS$_a but only visible within
   // the class.
   external get _a;
 }
@@ skipping 160 matching lines @@
     });
   });
 
   group('constructor', () {
     test('simple', () {
       var o = new ClassWithConstructor("foo", "bar");
       expect(o.a, equals("foo"));
       expect(o.b, equals("bar"));
       expect(o.getA(), equals("foo"));
     });
+    test('external factory', () {
+      var o = new ClassWithFactory("foo", "bar");
+      expect(o.a, equals("foo"));
+      expect(o.b, equals("bar"));
+      expect(o.getA(), equals("foo"));
+    });
   });
 
   group('private class', () {
     test('simple', () {
       var o = new _ClassWithConstructor("foo", "bar");
       expect(o.a, equals("foo"));
       expect(o.b, equals("bar"));
       expect(o.getA(), equals("foo"));
     });
   });
@@ skipping 223 matching lines @@
   group('html', () {
     test('return html type', () {
       expect(getCanvasContext() is CanvasRenderingContext2D, isTrue);
     });
     test('js path contains html types', () {
       expect(propertyOnWindow, equals(42));
       expect(propertyOnDocument, equals(45));
     });
   });
 }