Remove duplicated code between HttpIO and ChunkedIO

The following discussion from !18169 (merged) should be addressed:

@dosuken123 started a discussion:

We're gonna end up with a lot of duplication with HttpIO. Can we consider using https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18153 as it can easily adopt HttpIO?

Edited May 16, 2018 by Shinya Maeda