Instead of using two separate bits to encode three possible values, use
three values to encode the three possible values.

R=svenpanne@chromium.org
BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9372016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10654 ce2b1a6d-e550-0410-aec6-3dcde31c8c00