CrOS login: force subpixel anti-aliasing to stay off.
This is to make sure there're no artifacts during transitions.

BUG=302838
NOTRY=true

Review URL: https://codereview.chromium.org/26922005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228918 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228918