SPDY - add support for spdy/2.1 to support flow control.

SPDY - add support for spdy/2.1 to support flow control.

1) Add spdy/2.1 as a supported NPN protocol.
2) Advertise that chrome supports spdy/2.1 when --flow-control (spdy
flag) is enabled. 
3) When SPDY protocol is negotiated, enable flow_control in
spdy_session if spdy/2.1 is negotiated as NPN protocol. 

BUG=106911
R=willchan
TEST=network unit tests and if possible test with SPDY 2.1 server
with command line flag --flow-control.

This CL is same as the following CL. Implemented changes suggested
by willchan in the following review.
http://codereview.chromium.org/8890044/
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=113942

[ramant (doing other things), 2011-12-10 03:27:27]

Hi willchan,
  Sorry for the trouble. This CL is same as the following CL which you you have
lgtm'ed. Sync'ed with the tip.

http://codereview.chromium.org/8890044/

thanks,
raman

[willchan no longer on Chromium, 2011-12-10 03:34:22]

LGTM

On 2011/12/10 03:27:27, ramant wrote:
> Hi willchan,
>   Sorry for the trouble. This CL is same as the following CL which you you
have
> lgtm'ed. Sync'ed with the tip.
> 
> http://codereview.chromium.org/8890044/
> 
> thanks,
> raman

[commit-bot: I haz the power, 2011-12-10 04:49:12]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtenneti@chromium.org/8892026/1