anchor.diff:    String renamePrivateIdentifier(LibraryElement library, String id) =>
         getName(library, id, () => '_${privateNameCounter++}${id}');
   
  +  Generator topLevelGenerator =
  +      true ? conservativeGenerator : new MinifyingGenerator('ABCD').generate;
     String generateUniqueName(name) {
  -    while (usedTopLevelIdentifiers.contains(name)) name = 'p_$name';
  -    usedTopLevelIdentifiers.add(name);
  -    return name;
  +    String newName = topLevelGenerator(
  +        name, usedTopLevelIdentifiers.contains);
  +    usedTopLevelIdentifiers.add(newName);
  +    return newName;
     }
   
     String renameElement(Element element) {
  
positive.code:         });
    });
  }
  
negative.code:     return getName(library, originalName,
                     () => generateUniqueName(originalName));
    }
  
    placeholderCollector.nullNodes.forEach((Node node) {
      renames[node] = '';
  