Reapply change to update dart2js operator equals semantics to follow

lib/unittest/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.
 
 
 /**
  * Returns a matcher that matches empty strings, maps or collections.
  */
 final Matcher isEmpty = const _Empty();
 
@@ skipping 111 matching lines @@
     return reason;
   }
 
   Description _recursiveMatch(expected, actual, String location, int depth) {
     Description reason = null;
     // If _limit is 1 we can only recurse one level into object.
     bool canRecurse = depth == 0 || _limit > 1;
     if (expected == actual) {
       // Do nothing.
     } else if (depth > _limit) {
-      reason =  new StringDescription('recursion depth limit exceeded');
+      reason = new StringDescription('recursion depth limit exceeded');
     } else {
       if (expected is Iterable && canRecurse) {
         String r = _compareIterables(expected, actual,
           _recursiveMatch, depth+1);
         if (r != null) reason = new StringDescription(r);
       } else if (expected is Map && canRecurse) {
         if (actual is !Map) {
           reason = new StringDescription('expected a map');
         } else if (expected.length != actual.length) {
           reason = new StringDescription('different map lengths');
@@ skipping 438 matching lines @@
   final _matcher;
   final String _description;
 
   const _Predicate(this._matcher, this._description);
 
   bool matches(item) => _matcher(item);
 
   Description describe(Description description) =>
       description.add(_description);
 }