Revert of ipc: Add a member to IPC::Message::Header on Windows.

Revert of ipc: Add a member to IPC::Message::Header on Windows. (patchset #1 id:1 of https://codereview.chromium.org/1400713002/ )

Reason for revert:
Likely causes crashes:
https://code.google.com/p/chromium/issues/detail?id=527588#c57

Original issue's description:
> ipc: Add a member to IPC::Message::Header on Windows.
>
> According to my most recent debugging experiments, the root cause of the crashes
> that happened the first time I tried to make this change have magically
> disappeared. See the bug for more details.
>
> BUG=527588
>
> Committed: https://crrev.com/c32bea67c022c6c385463f0eec027f18b2915300
> Cr-Commit-Position: refs/heads/master@{#354889}

TBR=tsepez@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=527588
Committed: https://crrev.com/e2eeedbfaefbdd4a7aa48733aff7ae15ce831fb6
Cr-Commit-Position: refs/heads/master@{#355089}

[erikchen, 2015-10-20 17:21:23]

Created Revert of ipc: Add a member to IPC::Message::Header on Windows.

[commit-bot: I haz the power, 2015-10-20 17:22:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1414293002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1414293002/1

[commit-bot: I haz the power, 2015-10-20 17:23:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-20 17:24:12]

Patchset 1 (id:??) landed as
https://crrev.com/e2eeedbfaefbdd4a7aa48733aff7ae15ce831fb6
Cr-Commit-Position: refs/heads/master@{#355089}