Fixes cursor hiding bug

OnCursorVisibilityChanged may be invoked multiple times with the same
value. Current windows implementation is effectively ref counted. We
don't want that, instead it should show/hide based on most recent
call.

BUG=317496
TEST=none
R=ananta@chromium.org

Review URL: https://codereview.chromium.org/70383014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235500 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235500