Rename ascii to one-byte where applicable.

R=dcarney@chromium.org, marja@chromium.org

Review URL: https://codereview.chromium.org/559913002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23840 ce2b1a6d-e550-0410-aec6-3dcde31c8c00