Change backlog on http server listen from 5 to 128.

Change backlog on http server listen from 5 to 128.

5 simultaneously connecting clients seems like very little. This
also fixes an http client test on Mac. If the backlog is too
small a connection can be dropped again before it is accepted
and the client will get a "broken pipe" or "connection reset"
error.

R=sgjesse@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=11865

[Søren Gjesse, 2012-09-05 10:32:36]

lgtm

Should we perhaps add some additional comments on backlog in the documentation?

[Mads Ager (google), 2012-09-05 10:42:30]

On 2012/09/05 10:32:36, Søren Gjesse wrote:
> lgtm
> 
> Should we perhaps add some additional comments on backlog in the
documentation?

We could. I'm not sure what to put there though. The current documentation
refers to the OS listen setup. I think that is probably as detailed as we want
to get so we don't have to write a lot about how various OS implementations of
listen differ.