The new ParserCheckpoint mechanism resets some state, notably the
bailout ID counter but also some statement counters (only applicable
once we get "do" expressions) when we decide to reinterpret a comma
expression as arrow function arguments.

R=rossberg@chromium.org, marja@chromium.org
BUG=v8:3475
LOG=N

Review URL: https://codereview.chromium.org/443903003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22925 ce2b1a6d-e550-0410-aec6-3dcde31c8c00