Migrate test block 10 to Dart 2.0.

tests/corelib/iterable_expand_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:collection';
-
-class MyList extends ListBase {
-  List list;
-  MyList(this.list);
-
-  get length => list.length;
-  set length(val) {
-    list.length = val;
-  }
-
-  operator [](index) => list[index];
-  operator []=(index, val) => list[index] = val;
-
-  String toString() => "[" + join(", ") + "]";
-}
-
-main() {
-  test(expectation, iterable) {
-    Expect.listEquals(expectation, iterable.toList());
-  }
-
-  // Function not called on empty iterable.
-  test(
-      [],
-      [].expand((x) {
-        throw "not called";
-      }));
-
-  // Creating the iterable doesn't call the function.
-  [1].expand((x) {
-    throw "not called";
-  });
-
-  test([1], [1].expand((x) => [x]));
-  test([1, 2, 3], [1, 2, 3].expand((x) => [x]));
-
-  test([], [1].expand((x) => []));
-  test([], [1, 2, 3].expand((x) => []));
-  test([2], [1, 2, 3].expand((x) => x == 2 ? [2] : []));
-
-  test([1, 1, 2, 2, 3, 3], [1, 2, 3].expand((x) => [x, x]));
-  test([1, 1, 2], [1, 2, 3].expand((x) => [x, x, x].skip(x)));
-
-  test([1], new MyList([1]).expand((x) => [x]));
-  test([1, 2, 3], new MyList([1, 2, 3]).expand((x) => [x]));
-
-  test([], new MyList([1]).expand((x) => []));
-  test([], new MyList([1, 2, 3]).expand((x) => []));
-  test([2], new MyList([1, 2, 3]).expand((x) => x == 2 ? [2] : []));
-
-  test([1, 1, 2, 2, 3, 3], new MyList([1, 2, 3]).expand((x) => [x, x]));
-  test([1, 1, 2], new MyList([1, 2, 3]).expand((x) => [x, x, x].skip(x)));
-
-  // if function throws, iteration is stopped.
-  Iterable iterable = [1, 2, 3].expand((x) {
-    if (x == 2) throw "FAIL";
-    return [x, x];
-  });
-  Iterator it = iterable.iterator;
-  Expect.isTrue(it.moveNext());
-  Expect.equals(1, it.current);
-  Expect.isTrue(it.moveNext());
-  Expect.equals(1, it.current);
-  Expect.throws(it.moveNext, (e) => e == "FAIL");
-  // After throwing, iteration is ended.
-  Expect.equals(null, it.current);
-  Expect.isFalse(it.moveNext());
-}