dart2js: put all type-test related properties on the prototype and not on the constructor.

tests/language/mixin_only_for_rti_test.dart

Index: tests/language/mixin_only_for_rti_test.dart
diff --git a/tests/language/mixin_only_for_rti_test.dart b/tests/language/mixin_only_for_rti_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..4c2245a1654a448c433d77e0d3ca64eb7b92845c
--- /dev/null
+++ b/tests/language/mixin_only_for_rti_test.dart
@@ -0,0 +1,25 @@
+// Copyright (c) 2014, 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.
+
+import "package:expect/expect.dart";
+
+class Tester<T> {
+  testGenericType(x) {
+    return x is T;
+  }
+}
+
+abstract class A = B with C;
+class B {}
+class C {}
+
+class X extends Y with Z {}
+class Y {}
+class Z {}
+
+main() {
+  // Classes A and X are only used as generic arguments.
+  Expect.isFalse(new Tester<A>().testGenericType(new Object()));
+  Expect.isFalse(new Tester<X>().testGenericType(new Object()));
+}