Remove cancel and make crash exit with code 253.

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 "package:expect/expect.dart";
 import "../../../sdk/lib/_internal/compiler/implementation/scanner/scannerlib.dart";
 import "../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart";
 
 import "../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart"
     show DiagnosticListener,
@@ skipping 57 matching lines @@
   Node node = listener.popNode();
   Expect.isTrue(listener.nodes.isEmpty);
   return unparse(node);
 }
 
 class MessageCollector implements DiagnosticListener {
   List<String> messages;
   MessageCollector() {
     messages = [];
   }
-  void cancel(String reason, {node, token, instruction, element}) {
+  void internalError(node, String reason) {
     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,
-                      Element element}) {
-    throw message;
-  }
 }