anchor.diff:        NavigationTarget target = region.target;
         if (target.filePath != unitInfo.path || region.offset != target.offset) {
           String openInsertion = openInsertions[openOffset] ?? '';
  -        String htmlPath = pathMapper.map(target.filePath);
  +        String htmlPath = pathContext.relative(pathMapper.map(target.filePath),
  +            from: unitDir);
           openInsertion = '<a href="$htmlPath#o${target.offset}">$openInsertion';
           openInsertions[openOffset] = openInsertion;
   
  
positive.code: 
    /// Return the content of the file with navigation links and anchors added.
    String _computeNavigationContent(UnitInfo unitInfo) {
      String content = unitInfo.content;
      OffsetMapper mapper = unitInfo.offsetMapper;
      Map<int, String> openInsertions = {};
  
negative.code:   /// Creates an output object for the given library info.
    InstrumentationRenderer(this.unitInfo, this.migrationInfo, this.pathMapper);
  
    /// Return the path context used to manipulate paths.
    path.Context get pathContext => migrationInfo.pathContext;
  
    /// Builds an HTML view of the instrumentation information in [unitInfo].
    String render() {
      // TODO(brianwilkerson) Restore syntactic highlighting.
  