Remove Parser::scanner(). There is already ParserBase::scanner().

R=ulan@chromium.org
BUG=v8:3126
LOG=N

Review URL: https://codereview.chromium.org/166513003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19376 ce2b1a6d-e550-0410-aec6-3dcde31c8c00