Migrate test block 7 to Dart 2.0.

tests/corelib_strong/duration2_test.dart

-// Copyright (c) 2015, 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";
-
-main() {
-  // If the duration class multiplies "str" * microseconds-per-day (instead of
-  // (microseconds-per-day * "str") it will try to build up a huge string and
-  // terminate with an out-of-memory exception instead of an ArgumentError or
-  // TypeError.
-  // See dartbug.com/22309
-
-  String longString = "str" * 1000;
-  Expect.throws(() => new Duration(days: longString),
-      (e) => e is ArgumentError || e is TypeError || e is NoSuchMethodError);
-  Expect.throws(() => new Duration(hours: longString),
-      (e) => e is ArgumentError || e is TypeError || e is NoSuchMethodError);
-  Expect.throws(() => new Duration(minutes: longString),
-      (e) => e is ArgumentError || e is TypeError || e is NoSuchMethodError);
-  Expect.throws(() => new Duration(seconds: longString),
-      (e) => e is ArgumentError || e is TypeError || e is NoSuchMethodError);
-  Expect.throws(() => new Duration(milliseconds: longString),
-      (e) => e is ArgumentError || e is TypeError || e is NoSuchMethodError);
-  Expect.throws(() => new Duration(microseconds: longString),
-      (e) => e is ArgumentError || e is TypeError || e is NoSuchMethodError);
-}