Copy new JS Interop test from dev_compiler test suite.

tests/html/js_typed_interop_test.dart

Index: tests/html/js_typed_interop_test.dart
diff --git a/tests/html/js_typed_interop_test.dart b/tests/html/js_typed_interop_test.dart
index 960c0ccf453521c4f8999ef37dfc3b4a07c722aa..bbbd8677305a5907f0f502dac82aac544a314f8e 100644
--- a/tests/html/js_typed_interop_test.dart
+++ b/tests/html/js_typed_interop_test.dart
@@ -80,7 +80,7 @@ _injectJs() {
     _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]; };
@@ -144,6 +144,14 @@ class _ClassWithConstructor {
   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);
@@ -324,6 +332,12 @@ main() {
       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', () {