I think I need a *bridge Iteratee* to which write data, because ChunkedResult.chunks is not an Iteratee, ChunkedResult.chunks is a function which maps a Iteratee[A, Unit] to Unit.
The implementation of *bridge Iteratee* is considered in various way, for example, I can use `Channel` which comes from Concurrent.broadcast, but this time, I decided to use OutputStream which comes from Enumerator.outputStream.

I'm new of Iteratee/Enumerator, if you have a more concise and better way to map from ChunkedResult.chunks to Enumerator, tell me.

And also, the purpose of this patch is to improve testability of ChunkedResult.
In java, there is lack of testability of ChunkedResult.
the purpose of this patch is to extract all chunks from ChunkedResult.chunks and to extract a head chunk from ChunkedResult.chunks.
I want you to tell me if there is a more efficient way to achieve this purpose.