anchor.diff:    final ResolverImpl _resolver;
     _AssetUriResolver(this._resolver);
   
  -  Source resolveAbsolute(ContentCache contentCache, Uri uri) {
  +  Source resolveAbsolute(Uri uri) {
       var assetId = _resolve(null, uri.toString(), logger, null);
       var source = _resolver.sources[assetId];
       /// All resolved assets should be available by this point.
  
positive.code: 
    int get hashCode => _proxy.hashCode;
  
    void getContents(Source_ContentReceiver receiver) {
      _proxy.getContents(receiver);
    }
  
    String get encoding => _proxy.encoding;
  
  
negative.code:     var sourceFile = _getSourceFile(element);
      if (sourceFile == null) return null;
  
      return new TextEditTransaction(source.rawContents, sourceFile);
    }
  
    /// Gets the SourceFile for the source of the element.
  