Log out the user instead of locking the screen on TOUCH_UI builds.
Log out the user instead of locking the screen on TOUCH_UI builds.

The screen locker does not reliably work on TOUCH_UI builds. In order to effectively "lock" the screen we will sign out the user for now and later implement the lock screen in WebUI.

BUG=None
TEST=Tested locking the screen and observed it logging out.


Review URL: http://codereview.chromium.org/7888040

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@101127 0039d316-1c4b-4281-b951-d872f2087c98

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