Rename XMatching to XWhere.

tests/corelib/iterable_first_matching_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.
-
-main() {
-  List<int> list1 = <int>[1, 2, 3];
-  List<int> list2 = const <int>[4, 5];
-  List<String> list3 = <String>[];
-  Set<int> set1 = new Set<int>();
-  set1..add(11)
-      ..add(12)
-      ..add(13);
-  Set set2 = new Set();
-
-  Expect.equals(2, list1.firstMatching((x) => x.isEven));
-  Expect.equals(1, list1.firstMatching((x) => x.isOdd));
-  Expect.throws(() => list1.firstMatching((x) => x > 3),
-                (e) => e is StateError);
-  Expect.equals(null, list1.firstMatching((x) => x > 3, orElse: () => null));
-  Expect.equals(499, list1.firstMatching((x) => x > 3, orElse: () => 499));
-
-  Expect.equals(4, list2.firstMatching((x) => x.isEven));
-  Expect.equals(5, list2.firstMatching((x) => x.isOdd));
-  Expect.throws(() => list2.firstMatching((x) => x == 0),
-                (e) => e is StateError);
-  Expect.equals(null, list2.firstMatching((x) => false, orElse: () => null));
-  Expect.equals(499, list2.firstMatching((x) => false, orElse: () => 499));
-
-  Expect.throws(() => list3.firstMatching((x) => x == 0),
-                (e) => e is StateError);
-  Expect.throws(() => list3.firstMatching((x) => true), (e) => e is StateError);
-  Expect.equals(null, list3.firstMatching((x) => true, orElse: () => null));
-  Expect.equals("str", list3.firstMatching((x) => false, orElse: () => "str"));
-
-  Expect.equals(12, set1.firstMatching((x) => x.isEven));
-  var odd = set1.firstMatching((x) => x.isOdd);
-  Expect.isTrue(odd == 11 || odd == 13);
-  Expect.throws(() => set1.firstMatching((x) => false), (e) => e is StateError);
-  Expect.equals(null, set1.firstMatching((x) => false, orElse: () => null));
-  Expect.equals(499, set1.firstMatching((x) => false, orElse: () => 499));
-
-  Expect.throws(() => set2.firstMatching((x) => false), (e) => e is StateError);
-  Expect.throws(() => set2.firstMatching((x) => true), (e) => e is StateError);
-  Expect.equals(null, set2.firstMatching((x) => true, orElse: () => null));
-  Expect.equals(499, set2.firstMatching((x) => false, orElse: () => 499));
-}