Migrated test block 170 to Dart 2.0.

tests/lib_strong/async/intercept_print1_test.dart

-// Copyright (c) 2013, 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 'dart:async';
-import 'catch_errors.dart';
-
-var events = [];
-
-void printHandler1(Zone self, ZoneDelegate parent, Zone origin, String line) {
-  events.add("print: $line");
-}
-
-bool shouldIntercept = true;
-
-void printHandler2(Zone self, ZoneDelegate parent, Zone origin, String line) {
-  if (shouldIntercept) {
-    events.add("print **: $line");
-  } else {
-    parent.print(origin, line);
-  }
-}
-
-const TEST_SPEC1 = const ZoneSpecification(print: printHandler1);
-const TEST_SPEC2 = const ZoneSpecification(print: printHandler2);
-
-main() {
-  Zone zone1 = Zone.current.fork(specification: TEST_SPEC1);
-  Zone zone2 = zone1.fork(specification: TEST_SPEC2);
-  zone1.run(() {
-    print("1");
-    print(2);
-    print({
-      3: [4]
-    });
-  });
-  zone2.run(() {
-    print("5");
-    shouldIntercept = false;
-    print(6);
-  });
-  Expect.listEquals(
-      ["print: 1", "print: 2", "print: {3: [4]}", "print **: 5", "print: 6"],
-      events);
-}