Revert "Remove TypeToken as means for assigning type arguments to arrays."

compiler/lib/implementation/type_token.dart

Index: compiler/lib/implementation/type_token.dart
diff --git a/compiler/lib/implementation/type_token.dart b/compiler/lib/implementation/type_token.dart
new file mode 100644
index 0000000000000000000000000000000000000000..6d12be7afb94ccc895abe4e934ebc3b8ef4242f0
--- /dev/null
+++ b/compiler/lib/implementation/type_token.dart
@@ -0,0 +1,11 @@
+// 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.
+
+/*
+ * This class is generic. It's main use is to transfer type information from
+ * Dart to JS.
+ */
+class TypeToken<T> {
+  const TypeToken();
+}