Implement type cast in the VM.

tests/language/pseudo_kw_test.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.
 // Check that we can use pseudo keywords as names in function level code.
 
 
 class PseudoKWTest {
   static testMain() {
 
     // This is a list of built-in identifiers from the Dart spec.
     // It sanity checks that these pseudo-keywords are legal identifiers.
 
     var abstract = 0;
+    var as = 0;
     var assert = 0;
     var call = 0;
     var Dynamic = 0;
     var factory = 0;
     var get = 0;
     var implements = 0;
     var import = 0;
     var interface = 0;
     var library = 0;
     var negate = 0;
@@ skipping 80 matching lines @@
   Expect.equals(1, A.static());
   typedef("T");
   Expect.equals("typedef T", typedef("T"));
   static("true");
   Expect.equals(false, static("true"));
   Expect.equals(5, C.operator);
   Expect.equals(null, C.get);
   C.set = 0;
   Expect.equals(111, C.set);
 }