Revert of Remote assistance on Chrome OS Part V - It2MeHost Continue Window

Revert of Remote assistance on Chrome OS Part V - It2MeHost Continue Window (patchset #5 id:120001 of https://codereview.chromium.org/690183002/)

Reason for revert:
Build failure on
http://build.chromium.org/p/chromium.chromiumos/buildstatus?builder=Linux%20ChromiumOS%20Builder%20%28dbg%29&number=54095

Original issue's description:
> Remote assistance on Chrome OS Part V - It2MeHost Continue Window
>
> This CL implements the ContinueWindow on ChromeOS, which will
> be shown to the user for confirmation after 10 minutes into a Remote
> Assistance session.
>
> To implement the ContinueWindow, this CL introduces a new class
> MessageBox, which is a re-usable component built on top of the
> widget framework.
>
> BUG=424908
>
> Committed: https://crrev.com/6410d7ad4937a4a86e9ad28b9ecf99f961305b2d
> Cr-Commit-Position: refs/heads/master@{#302657}

TBR=wez@chromium.org,dcaiafa@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=424908
Committed: https://crrev.com/71ffa2147e36e87212d2a1e0c56d47cdc77a8410
Cr-Commit-Position: refs/heads/master@{#302660}

[kelvinp, 2014-11-04 20:54:31]

Created Revert of Remote assistance on Chrome OS Part V - It2MeHost Continue
Window

[commit-bot: I haz the power, 2014-11-04 20:55:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/689093004/1

[commit-bot: I haz the power, 2014-11-04 20:57:23]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-04 20:58:00]

Patchset 1 (id:??) landed as
https://crrev.com/71ffa2147e36e87212d2a1e0c56d47cdc77a8410
Cr-Commit-Position: refs/heads/master@{#302660}