Fix end_to_end_test performance regression caused by using mutexes

Fix end_to_end_test performance regression caused by using mutexes
instead of notifications in server_thread. Testing only.

Merge internal change: 59322530

Reversed pause/resume changes of server_thread in the following CL:
https://codereview.chromium.org/127503002/

R=rch@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243948

[Ryan Hamilton, 2014-01-09 16:36:19]

LGTM.  Are you going to include this in your "merge QUIC changes" CL?

[commit-bot: I haz the power, 2014-01-09 16:45:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtenneti@chromium.org/132073002/1

[ramant (doing other things), 2014-01-09 16:46:40]

On 2014/01/09 16:36:19, Ryan Hamilton wrote:
> LGTM.  Are you going to include this in your "merge QUIC changes" CL?

Hope you don't mind if I submit this CL by itself to fix the memory bot.

thanks
raman

[Ryan Hamilton, 2014-01-09 16:55:24]

On 2014/01/09 16:46:40, ramant wrote:
> On 2014/01/09 16:36:19, Ryan Hamilton wrote:
> > LGTM.  Are you going to include this in your "merge QUIC changes" CL?
> 
> Hope you don't mind if I submit this CL by itself to fix the memory bot.
> 
> thanks
> raman

LGTM.  Go for it!

[commit-bot: I haz the power, 2014-01-09 19:13:13]

Change committed as 243948