Revert 251146 "Disable ubercomp for kiosk mode."

> Disable ubercomp for kiosk mode.
> 
> This is a short term workaround. Will revert promptly.
> 
> BUG=342061
> TEST=launch app in kiosk mode and make sure things are still working, and RenderWidget::CreateOutputSurface() does not allocate DelegatedCompositorOutputSurface.
> R=xiyuan@chromium.org
> 
> Review URL: https://codereview.chromium.org/164683002

TBR=hshi@chromium.org

Review URL: https://codereview.chromium.org/165243002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251184 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251184