Remove deprecated Strings class.

utils/apidoc/html_diff.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.
 
 /**
  * A script to assist in documenting the difference between the dart:html API
  * and the old DOM API.
  */
 library html_diff;
 
@@ skipping 179 matching lines @@
       domNames.forEach((name) {
         var nameMembers = _membersFromName(name, domTypes);
         if (nameMembers.isEmpty) {
           if (name.contains('.')) {
             warn('no member $name');
           } else {
             final options = <String>[];
             for (var t in domTypes) {
               options.add('$t.$name');
             }
-            Strings.join(options, ' or ');
+            options.join(' or ');
             warn('no member $options');
           }
         }
         members.addAll(nameMembers);
       });
       return members;
     }
 
     return new Set();
   }
@@ skipping 17 matching lines @@
       return members;
     }
 
     if (name.split('.').length != 2) {
       warn('invalid member name ${name}');
       return new Set();
     }
     return new Set.from([name]);
   }
 }