Revert of [mojo-edk] Serialise windows handles into an "extra header" section.

Revert of [mojo-edk] Serialise windows handles into an "extra header" section. (patchset #3 id:40001 of https://codereview.chromium.org/1740953002/ )

Reason for revert:
Reverting per ARC++ request. Let's reland in a way that doesn't affect non-OSX POSIX. :|

Original issue's description:
> [mojo-edk] Serialise windows handles into an "extra header" section.
>
> This change introduces an "extra header" section of a channel message
> header. On windows, platform handles are place into this section instead
> of being appended to the end of a message.
>
> At the same time, make a couple of smaller changes:
> 1. Allow the number of serialised handles to be less than the number
> stated in the constructor.
> 2. Add a has_mach_ports() helper function.
> 3. Limit the number of attached handles.
>
> These changes are all prep work for Mach ports support.
>
> BUG=582468
>
> Committed: https://crrev.com/fbebd41187198e7782b3fec9ddf9f155b9df1789
> Cr-Commit-Position: refs/heads/master@{#378099}

TBR=amistry@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=582468
Committed: https://crrev.com/b49df35e75dab5406defaf166c9448fd3eaf7a26
Cr-Commit-Position: refs/heads/master@{#378530}

[Ken Rockot(use gerrit already), 2016-03-01 18:31:09]

Created Revert of [mojo-edk] Serialise windows handles into an "extra header"
section.

[commit-bot: I haz the power, 2016-03-01 18:32:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1753723003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1753723003/1

[commit-bot: I haz the power, 2016-03-01 19:03:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1753723003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1753723003/1

[commit-bot: I haz the power, 2016-03-01 19:31:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1753723003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1753723003/1

[commit-bot: I haz the power, 2016-03-01 19:43:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-01 19:45:59]

Description was changed from

==========
Revert of [mojo-edk] Serialise windows handles into an "extra header" section.
(patchset #3 id:40001 of https://codereview.chromium.org/1740953002/ )

Reason for revert:
Reverting per ARC++ request. Let's reland in a way that doesn't affect non-OSX
POSIX. :|

Original issue's description:
> [mojo-edk] Serialise windows handles into an "extra header" section.
> 
> This change introduces an "extra header" section of a channel message
> header. On windows, platform handles are place into this section instead
> of being appended to the end of a message.
> 
> At the same time, make a couple of smaller changes:
> 1. Allow the number of serialised handles to be less than the number
> stated in the constructor.
> 2. Add a has_mach_ports() helper function.
> 3. Limit the number of attached handles.
> 
> These changes are all prep work for Mach ports support.
> 
> BUG=582468
> 
> Committed: https://crrev.com/fbebd41187198e7782b3fec9ddf9f155b9df1789
> Cr-Commit-Position: refs/heads/master@{#378099}

TBR=amistry@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=582468
==========

to

==========
Revert of [mojo-edk] Serialise windows handles into an "extra header" section.
(patchset #3 id:40001 of https://codereview.chromium.org/1740953002/ )

Reason for revert:
Reverting per ARC++ request. Let's reland in a way that doesn't affect non-OSX
POSIX. :|

Original issue's description:
> [mojo-edk] Serialise windows handles into an "extra header" section.
>
> This change introduces an "extra header" section of a channel message
> header. On windows, platform handles are place into this section instead
> of being appended to the end of a message.
>
> At the same time, make a couple of smaller changes:
> 1. Allow the number of serialised handles to be less than the number
> stated in the constructor.
> 2. Add a has_mach_ports() helper function.
> 3. Limit the number of attached handles.
>
> These changes are all prep work for Mach ports support.
>
> BUG=582468
>
> Committed: https://crrev.com/fbebd41187198e7782b3fec9ddf9f155b9df1789
> Cr-Commit-Position: refs/heads/master@{#378099}

TBR=amistry@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=582468

Committed: https://crrev.com/b49df35e75dab5406defaf166c9448fd3eaf7a26
Cr-Commit-Position: refs/heads/master@{#378530}
==========

[commit-bot: I haz the power, 2016-03-01 19:46:00]

Patchset 1 (id:??) landed as
https://crrev.com/b49df35e75dab5406defaf166c9448fd3eaf7a26
Cr-Commit-Position: refs/heads/master@{#378530}