Use system-qwerty for accessbility virtual keyboard

BUG=339207
R=finnur@chromium.org, kevers@chromium.org

Review URL: https://codereview.chromium.org/132963010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248289 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248289