Migrate block 163 to Dart 2.0.

tests/language_strong/unhandled_exception_negative_test.dart

-// 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.
-// Dart test program for testing unhandled exceptions.
-
-class MyException {
-  const MyException(String message = "") : message_ = message;
-  String getMessage() { return message_; }
-  final String message_;
-}
-
-class Helper {
-  static int f1(int i) {
-    int j;
-    j = i + 200;
-    j = j + 300;
-    throw new MyException("Unhandled Exception");
-    return i;
-  }
-}
-
-class UnhandledExceptionNegativeTest {
-  static testMain() {
-    Helper.f1(1);
-  }
-}
-
-main() {
-  UnhandledExceptionNegativeTest.testMain();
-}