private List<File> findNewFiles(File directory, Set<File> existing, boolean recurse) {
    List<File> result = new ArrayList<>();
    findNewFiles(directory, existing, recurse, result);
    return result;
  }
Test the iterator returned is ok and deletion through the iterator is ok too. This is the
required functionality that eviction needs.

@throws Exception
imagepipeline-base/src/test/java/com/facebook/cache/disk/DefaultDiskStorageTest.java