Revert of Implement IPC::ParamTraits<mojo::MessagePipeHandle>

Revert of Implement IPC::ParamTraits<mojo::MessagePipeHandle> (patchset #4 id:60001 of https://codereview.chromium.org/1051443003/)

Reason for revert:
This broke the tests again, looks like ParamTraitInvalidMesssagePipe was fixed, but ParamTraitValidMessagePipe wasn't.

https://build.chromium.org/p/chromium.win/builders/XP%20Tests%20%281%29/builds/36687/steps/ipc_mojo_unittests/logs/IPCChannelMojoTest.ParamTraitValidMessagePipe

https://build.chromium.org/p/chromium.win/builders/XP%20Tests%20%281%29/builds/36687

Original issue's description:
> Implement IPC::ParamTraits<mojo::MessagePipeHandle>
>
> This allows MessagePipeHandle to be an IPC message member.
> Note that this assumes underlying channel being a ChannelMojo
> and can be used in content/  only after ChannelMojo settles.
>
> BUG=448190
> TEST=IPCChannelMojoTest.ParamTrait*
> R=viettrungluu@chromium.org
>
> Committed: https://crrev.com/5656ae68841a3e3ddaac75cf2983d9052d71d0d5
> Cr-Commit-Position: refs/heads/master@{#323265}
>
> Committed: https://crrev.com/2b85d21119ce534940ccd2ff57727cd4b428081c
> Cr-Commit-Position: refs/heads/master@{#323370}

TBR=viettrungluu@chromium.org,morrita@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=448190
Committed: https://crrev.com/ef026b654f3e8e0d6f83114bf0f148b26a5cc1be
Cr-Commit-Position: refs/heads/master@{#323484}

[mfomitchev, 2015-04-02 14:49:42]

Created Revert of Implement IPC::ParamTraits<mojo::MessagePipeHandle>

[commit-bot: I haz the power, 2015-04-02 14:50:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1054983003/1

[commit-bot: I haz the power, 2015-04-02 14:51:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-03 20:25:21]

Patchset 1 (id:??) landed as
https://crrev.com/ef026b654f3e8e0d6f83114bf0f148b26a5cc1be
Cr-Commit-Position: refs/heads/master@{#323484}