Port r13375 (198859e8)

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

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/11969004
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13390 ce2b1a6d-e550-0410-aec6-3dcde31c8c00