Fix break location calculation.

R=ulan@chromium.org
BUG=chromium:419663
LOG=Y

Review URL: https://codereview.chromium.org/658723005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24697 ce2b1a6d-e550-0410-aec6-3dcde31c8c00