ash: Make sure the cursor is locked when shutdown is requested.

If a mouse is moved during a shutdown in the login/lock screen, then the
mouse move event should not make the cursor visible. This currently doesn't
work quite right, as the cursor is not 'locked'. The test for it happens to
get the correct result currently because there is no window in the lockscreen
to receive the event, and so the event is never dispatched, causing the
cursor to remain hidden. But there are windows that receive events in the
lockscreen during normal runtime. So fix the issue by locking the cursor when
requesting shutdown, and update the test accordingly.

BUG=none
R=oshima@chromium.org

Review URL: https://codereview.chromium.org/137523002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244815 0039d316-1c4b-4281-b951-d872f2087c98
Removes duplicated include.

R=ben@chromium.org
TBR=ben@chromium.org
BUG=none

Review URL: https://codereview.chromium.org/136793011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244816 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244816