TBR: Removed const from CustomMatcher constructor. dartc doesn't like it.

pkg/unittest/lib/src/core_matchers.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.
 
 part of matcher;
 
 /**
  * Returns a matcher that matches empty strings, maps or iterables
  * (including collections).
  */
@@ skipping 690 matching lines @@
  *
  * and then use this for example like:
  *
  *      expect(inventoryItem, new HasPrice(greaterThan(0)));
  */
 class CustomMatcher extends BaseMatcher {
   final String _featureDescription;
   final String _featureName;
   final Matcher _matcher;
 
-  const CustomMatcher(this._featureDescription, this._featureName, matcher)
+  CustomMatcher(this._featureDescription, this._featureName, matcher)
       : this._matcher = wrapMatcher(matcher);
 
   /** Override this to extract the interesting feature.*/
   featureValueOf(actual) => actual;
 
   bool matches(item, MatchState matchState) {
     var f = featureValueOf(item);
     if (_matcher.matches(f, matchState)) return true;
     matchState.state = { 'innerState': matchState.state, 'feature': f };
     return false;
   }
 
   Description describe(Description description) =>
       description.add(_featureDescription).add(' ').addDescriptionOf(_matcher);
 
   Description describeMismatch(item, Description mismatchDescription,
                                MatchState matchState, bool verbose) {
     mismatchDescription.add(_featureName).add(' ');
     _matcher.describeMismatch(matchState.state['feature'], mismatchDescription,
         matchState.state['innerState'], verbose);
     return mismatchDescription;
   }
 }