Add Dart_Null, Dart_True, and Dart_False.

runtime/vm/dart_api_state.cc

Index: runtime/vm/dart_api_state.cc
===================================================================
--- runtime/vm/dart_api_state.cc	(revision 0)
+++ runtime/vm/dart_api_state.cc	(revision 0)
@@ -0,0 +1,15 @@
+// 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.
+
+#include "vm/dart_api_state.h"
+
+namespace dart {
+
+// A distinguished callback which indicates that a persistent handle
+// should not be deleted from the dart api.
+void ProtectedHandleCallback() {
+  // Do nothing.
+}
+
+}  // namespace dart