Reland 54771 (and 54795) To enable TCP Preconnection by default...

Reland 54771 (and 54795) To enable TCP Preconnection by default

I pulled out the code to update the socket connectivity stats.

I added defensive code which should preclude the crash that 
was reported on the stability bot.

I added a second call to update the stats from
~ClientSocketHandle to ensure that we updated the
related ClientSocket when we are torn down.

As noted in the original checkin:

Enable speculative preconnection by default

Added histogram to track preconnection utilization (vs waste).

BUG=42694
r=mbelshe

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=55197

[jar (doing other things), 2010-08-05 23:20:16]

Hopefully, three times is the charm.

The changes from the last attempted landing are, as noted, localized in
client_socket_handle.*.  They involve the destructor, and calling to the new
function that handles updates of the related socket.

Thanks in advance,

Jim

[Mike Belshe, 2010-08-06 06:53:36]

lgtm