Add runtimeType() to Object which returns canonicalized instances of Type.

tests/language/first_class_types.dart

+// Copyright (c) 2012, 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 C<T> {}
+
+sameType(a, b) {
+  Expect.isTrue(a.runtimeType() === b.runtimeType());
+}
+
+differentType(a, b) {
+  Expect.isFalse(a.runtimeType() === b.runtimeType());
+}
+
+main() {
+  var v1 = new C<int>();
+  var v2 = new C<int>();
+  sameType(v1, v2);
+
+  var v3 = new C<num>();
+  differentType(v1, v3);
+
+  var i = 1;
+  var s = 'string';
+  var d = 3.14;
+  sameType(2, i);
+  sameType('hest', s);
+  sameType(1.2, d);
+
+  var l = [1, 2, 3];
+  var m = {'a': 1, 'b': 2};
+  sameType([], l);
+  sameType({}, m);
+}