Added 'dynamic' keyword, so that 'Dynamic' can be deprecated.

tests/compiler/dart2js/unparser2_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.
 
 #import("../../../lib/compiler/implementation/scanner/scannerlib.dart");
 #import("../../../lib/compiler/implementation/elements/elements.dart"); // only need CompilationUnitElement
 #import("../../../lib/compiler/implementation/tree/tree.dart");
 #import("../../../lib/compiler/implementation/leg.dart"); // only need DiagnosticListener & Script
 
 main() {
@@ skipping 57 matching lines @@
     messages.add(reason);
     throw reason;
   }
   void log(message) {
     messages.add(message);
   }
   void internalErrorOnElement(Element element, String message) {
     throw message;
   }
   void internalError(String message,
-                     [Node node, Token token, Dynamic instruction,
+                     [Node node, Token token, dynamic instruction,
                       Element element]) {
     throw message;
   }
 }