Refactoring in anticipation of handling variable bounds.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/18415005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15625 ce2b1a6d-e550-0410-aec6-3dcde31c8c00