This is mostly a rollback of r12966
[Make kAsciiDataHintTag have correct semantics for all both 1 and 2 byte string types.]

R=yangguo@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/11857015
Patch from Dan Carney <dcarney@google.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13375 ce2b1a6d-e550-0410-aec6-3dcde31c8c00