anchor.diff:        result.add(new _Asset(
           base: '${ArtifactStore.flutterRoot}/bin/cache/artifacts/material_fonts',
           source: path.basename(assetKey),
  -        key: assetKey
  +        relativePath: assetKey
         ));
       }
     }
  
positive.code:       result[baseAsset] = variants;
  
        // Find asset variants
        String assetPath = path.join(baseAsset.base, baseAsset.key);
        String assetFilename = path.basename(assetPath);
        Directory assetDir = new Directory(path.dirname(assetPath));
  
  
negative.code:   for (_Asset main in assets.keys) {
      List<String> variants = <String>[];
      for (_Asset variant in assets[main])
        variants.add(variant.relativePath);
      json[main.relativePath] = variants;
    }
    return new ZipEntry.fromString('AssetManifest.json', JSON.encode(json));
  }
  