[MINOR] http: partially revert the chunking optimization for now

Commit 57f5c1 used to provide a nice improvement on chunked encoding since
it ensured that we did not set a PUSH flag for every chunk or buffer data
part of a chunked transfer.

Some applications appear to erroneously abuse HTTP chunking in order to
get interactive exchanges between a user agent and an origin server with
very small chunks. While it happens to work through haproxy, it's terribly
slow due to the latency added after passing each chunk to the system, who
could wait up to 200ms before pushing them onto the wire.

So we need an interactive mode for such usages. In the mean time, step back
on the optim, but not completely, so that we still keep the flag as long as
we know we're not finished with the current chunk.

This change should be backported to 1.4 too as the issue was discovered
with it.
1 file changed