Revert of CHECK() if Windows non-blocking connect returns 0.

Revert of CHECK() if Windows non-blocking connect returns 0. (patchset #1 id:1 of https://codereview.chromium.org/1055813006/)

Reason for revert:
It's crashing in Canary builds. We have probably gained enough data now, so I'm reverting.

Original issue's description:
> CHECK() if Windows non-blocking connect returns 0.
>
> Non-blocking connect() on Windows is documented as always returning
> WSAEWOULDBLOCK or another error.
>
> There has been code in place to handle a 0 return value, but we have
> no way to test whether it is correct or not.
>
> Replace the code to handle a 0 return with a CHECK() call, to find out
> whether a 0 result really can happen or not.
>
> BUG=436634
> TEST=net_unittests
>
> Committed: https://crrev.com/2d53a9381e88eab543cc4c9fd122b0b1ed4f41d7
> Cr-Commit-Position: refs/heads/master@{#326243}

TBR=mmenke@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=436634
Committed: https://crrev.com/1a285faf58a6bac870e394569258818958f812f8
Cr-Commit-Position: refs/heads/master@{#326507}

[Adam Rice, 2015-04-23 14:05:33]

Created Revert of CHECK() if Windows non-blocking connect returns 0.

[commit-bot: I haz the power, 2015-04-23 14:06:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1076093006/1

[commit-bot: I haz the power, 2015-04-23 14:06:48]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-23 14:08:08]

Patchset 1 (id:??) landed as
https://crrev.com/1a285faf58a6bac870e394569258818958f812f8
Cr-Commit-Position: refs/heads/master@{#326507}