Fix socket usage in forwarder2.

Fix socket usage in forwarder2.

This fixes the use of *blocking* sockets in a non-blocking fashion (with
select()) and adds the new NonBlocking{Read,Write}() methods that will be used
in a follow-up CL.

BUG=313809
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=234937

[Philippe, 2013-11-13 09:45:52]

FYI, this is a preliminary CL. Marcus, remember that place with the select()
appearing to deadlock? It seems indeed to be an issue on the forwarder side. I
came across this hard to reproduce deadlock (during net_unittests) while working
on the other CL (making the controllers' deletion synchronous).

Just to be clear, this CL doesn't fix the deadlock itself but make it possible
to fix it with a follow-up CL. I can't fix it in this CL itself since this will
depend on the other CL.

[digit1, 2013-11-13 10:28:36]

lgtm

[digit1, 2013-11-13 10:28:41]

https://codereview.chromium.org/68893013/diff/1/tools/android/forwarder2/sock...
File tools/android/forwarder2/socket.cc (right):

https://codereview.chromium.org/68893013/diff/1/tools/android/forwarder2/sock...
tools/android/forwarder2/socket.cc:335: DCHECK(fcntl(socket_, F_GETFL) &
O_NONBLOCK);
I really like this DCHECK(), thanks :)

[commit-bot: I haz the power, 2013-11-13 14:55:13]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pliard@chromium.org/68893013/1

[commit-bot: I haz the power, 2013-11-13 22:44:51]

Change committed as 234937

[bulach, 2013-11-14 16:57:30]

lgtm (sorry, was perf sheriffing...)