Fix type masks for js-interop types.

tests/html/js_typed_interop_type3_test.dart

+import 'dart:html';
+import 'package:js/js.dart';
+import 'package:expect/expect.dart';
+
+@JS()
+class A {
+  external get foo;
+
+  external A(var foo);
+}
+
+@JS()
+@anonymous
+class C {
+  final foo;
+
+  external factory C({foo});
+}
+
+@JS()
+@anonymous
+class D {
+  final foo;
+
+  external factory D({foo});
+}
+
+class F {
+  final foo;
+
+  F(this.foo);
+}
+
+@NoInline()
+testA(A o) {
+  return o.foo;
+}
+
+@NoInline()
+testC(C o) {
+  return o.foo;
+}
+
+
+@NoInline()
+testD(D o) {
+  return o.foo;
+}
+
+@NoInline()
+testF(F o) {
+  return o.foo;
+}
+
+
+_injectJs() {
+  document.body.append(new ScriptElement()
+    ..type = 'text/javascript'
+    ..innerHtml = r"""
+function A(foo) {
+  this.foo = foo;
+}
+""");
+}
+
+void expectValueOrTypeError(f(), value) {
+  try {
+    String i = 0; // Test for checked mode.
+    Expect.equals(f(), value);
+  } on TypeError catch (error) {
+    Expect.throws(f, (ex) => ex is TypeError);
+  }
+}
+
+main() {
+  _injectJs();
+
+  var a = new A(1);
+  var d = new D(foo: 4);
+
+  Expect.equals(testA(a), 1); /// 01: ok
+  Expect.equals(testA(a), 1); /// 02: ok
+  Expect.equals(testA(d), 4);
+  Expect.equals(testD(d), 4); /// 02: continued
+}
+
+