Added ability to disable logging in mocks, to avoid the memory overhead if you don't need behavior …

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 148 matching lines @@
         // expect() will show it for us.
         reason = new StringDescription();
         if (depth > 1) {
           reason.add('expected ').addDescriptionOf(expected).add(' but was ').
               addDescriptionOf(actual);
         } else {
           reason.add('was ').addDescriptionOf(actual);
         }
       }
     }
-    if (reason != null) {
+    if (reason != null && location.length > 0) {
       reason.add(' ').add(location);
     }
     return reason;
   }
 
   String _match(expected, actual) {
     Description reason = _recursiveMatch(expected, actual, '', 0);
     return reason == null ? null : reason.toString();
   }
 
@@ skipping 407 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);
 }