Reapply "Add some failing (in Dart2Js) tests."

tests/language/src/Operator4Test.dart

+// Copyright (c) 2011, 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.
+
+class A {
+  operator <(other) => 1;
+}
+
+// This triggered a bug in Dart2Js: relational operators were not correctly
+// boolified.
+foo(a) {
+  try {
+    if (a < a) {
+      return "bad";
+    } else {
+      return 499;
+    }
+  } catch(TypeError e) {
+    return 499;
+  }
+}
+
+main() {
+  Expect.equals(499, foo(new A()));
+}