Re-apply "Remove unittest and matcher from the repo."

pkg/matcher/lib/src/util.dart

-// Copyright (c) 2014, 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.
-
-library matcher.util;
-
-import 'core_matchers.dart';
-import 'interfaces.dart';
-
-/// Useful utility for nesting match states.
-void addStateInfo(Map matchState, Map values) {
-  var innerState = new Map.from(matchState);
-  matchState.clear();
-  matchState['state'] = innerState;
-  matchState.addAll(values);
-}
-
-/// Takes an argument and returns an equivalent [Matcher].
-///
-/// If the argument is already a matcher this does nothing,
-/// else if the argument is a function, it generates a predicate
-/// function matcher, else it generates an equals matcher.
-Matcher wrapMatcher(x) {
-  if (x is Matcher) {
-    return x;
-  } else if (x is Function) {
-    return predicate(x);
-  } else {
-    return equals(x);
-  }
-}