Add VM internal Dart class 'ClassID' used to manage class-ids of known classes. Next CL: add consta…

runtime/lib/class_id.dart

Index: runtime/lib/class_id.dart
===================================================================
--- runtime/lib/class_id.dart	(revision 0)
+++ runtime/lib/class_id.dart	(working copy)
@@ -0,0 +1,7 @@
+// 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.
+
+class ClassID {
+  static int getID(Object value) native "ClassID_getID";
+}