Implement is-checks against type variables.

tests/language/generic_native_test.dart

+// Copyright (c) 2013, 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.
+
+// Test is-tests with type variables on native subclasses.
+
+class A<T> {
+  foo(o) => o is T;
+}
+
+class B {}
+
+class C {}
+
+main() {
+  Expect.isTrue(new A<Iterable<B>>().foo(new List<B>()));
+  Expect.isFalse(new A<Iterable<C>>().foo(new List<B>()));
+
+  Expect.isTrue(new A<Collection<B>>().foo(new List<B>()));
+  Expect.isFalse(new A<Collection<C>>().foo(new List<B>()));
+
+  Expect.isTrue(new A<Pattern>().foo('hest'));
+
+  Expect.isTrue(new A<Comparable<String>>().foo('hest'));
+  Expect.isFalse(new A<Comparable<C>>().foo('hest'));
+}